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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Angles d'Euler</span></h1>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="fr" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="fr" dir="ltr"><p>En <a href="M%C3%A9canique_(science)" title="Mécanique (science)">mécanique</a> et en <a href="Math%C3%A9matiques" title="Mathématiques">mathématiques</a>, les <b>angles d'Euler</b> sont les trois <a href="Angle" title="Angle">angles</a> qui donnent l'orientation d'un <a href="Mod%C3%A8le_du_solide_ind%C3%A9formable" title="Modèle du solide indéformable">solide</a> par rapport à un <a href="Tri%C3%A8dre" title="Trièdre">trièdre</a> cartésien de référence<sup id="cite_ref-TailletVillainFebvre201830''<abbr_class="abbr_"_title="sub_verbo_(«_à_l'article_»)"_>s.v.</abbr>''angles_d'Euler_1-0" class="reference"><a href="#cite_note-TailletVillainFebvre201830''<abbr_class="abbr_"_title="sub_verbo_(«_à_l'article_»)"_>s.v.</abbr>''angles_d'Euler-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>. Ils sont introduits par <a href="Leonhard_Euler" title="Leonhard Euler">Leonhard Euler</a> (<a href="1707_en_science" title="1707 en science">1707</a>-<a href="1783_en_science" title="1783 en science">1783</a>). Ils sont appelés, respectivement, <b>angle de <a href="Pr%C3%A9cession" title="Précession">précession</a></b>, <b>de <a href="Nutation" title="Nutation">nutation</a></b> et <b>de rotation propre</b><sup id="cite_ref-Pérez2014<abbr_class="abbr_"_title="21"_><span_class="romain"_style="text-transform:lowercase;_font-variant:normal;">xxi</span></abbr>_et_275_2-0" class="reference"><a href="#cite_note-Pérez2014<abbr_class="abbr_"_title="21"_><span_class="romain"_style="text-transform:lowercase;_font-variant:normal;">xxi</span></abbr>_et_275-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup class="reference cite_virgule">,</sup><sup id="cite_ref-TailletVillainFebvre201830''<abbr_class="abbr_"_title="sub_verbo_(«_à_l'article_»)"_>s.v.</abbr>''angles_d'Euler_1-1" class="reference"><a href="#cite_note-TailletVillainFebvre201830''<abbr_class="abbr_"_title="sub_verbo_(«_à_l'article_»)"_>s.v.</abbr>''angles_d'Euler-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>, les deux premiers pouvant être vus comme une généralisation des deux angles des <a href="Coordonn%C3%A9es_sph%C3%A9riques" title="Coordonnées sphériques">coordonnées sphériques</a>.
</p><p>Le mouvement d'un solide est la variation temporelle de sa position par rapport à un référentiel. Il peut être décrit en donnant la variation temporelle de six nombres scalaires, qui mesurent à la fois la position d'un de ses points (par exemple, son <a href="Centre_de_masse" class="mw-redirect" title="Centre de masse">centre de masse</a>) et l'orientation de ce solide : les trois angles d'Euler, <abbr class="abbr" title="confer (reportez-vous à/comparez avec)">cf.</abbr> schémas ci-dessous.
</p><p>Les angles d'Euler peuvent aussi servir à représenter l'<a href="Orientation_dans_l'espace" title="Orientation dans l'espace">orientation</a> d'un solide par rapport à un repère (appelée aussi <a href="Attitude_(astronautique)" class="mw-redirect" title="Attitude (astronautique)">attitude</a> en astronautique).
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<div class="gallerytext">Angles d'Euler <i>ψ</i>, <i>θ</i> et <i>φ</i>. Le référentiel fixe <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Oxyz}">
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<mi>O</mi>
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<annotation encoding="application/x-tex">{\displaystyle Oxyz}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/be27c2ad2be5d640cfc2a530df87d9b7b4ebf615.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:5.347ex; height:2.509ex;" alt="{\displaystyle Oxyz}" loading="lazy"></span> est indiqué en noir, le référentiel mobile <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Ox'y'z'}">
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<annotation encoding="application/x-tex">{\displaystyle Ox'y'z'}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/71746309c2b419fd19cc5f94603fd7118f0628ea.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:7.408ex; height:2.843ex;" alt="{\displaystyle Ox'y'z'}" loading="lazy"></span>en rouge et la ligne des nœuds <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Ou}">
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/724ba95bd28736236bd6589162c06618d2f4b503.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:3.103ex; height:2.176ex;" alt="{\displaystyle Ou}" loading="lazy"></span> en bleu.</div>
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<div class="thumb" style="width: 430px; height: 230px;"><span typeof="mw:File"></span></div>
<div class="gallerytext">Autre représentation.</div>
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<div class="mw-heading mw-heading2"><h2 id="Notations_et_étymologies"><span id="Notations_et_.C3.A9tymologies"></span>Notations et étymologies</h2></div>
<p>Les trois angles d'Euler, de précession, de nutation et de rotation propre (ou de giration), sont couramment notés respectivement <span class="texhtml mvar" style="font-style:italic;">ψ</span>, <span class="texhtml mvar" style="font-style:italic;">θ</span> et <span class="texhtml mvar" style="font-style:italic;">φ</span>.
</p><p>Le mot <i>précession</i> vient du latin <i>praecessio</i> (« action de précéder ») ; cela provient de son utilisation en astronomie dans l'expression « <a href="Pr%C3%A9cession_des_%C3%A9quinoxes" title="Précession des équinoxes">précession des équinoxes</a> ».
</p><p>Le mot <i>nutation</i> vient du latin <i>nutatio</i> (« action de pencher la tête ») et est aussi utilisé en botanique pour signifier l'habitude qu’ont certaines plantes de pencher leurs fleurs<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>.
</p><p>Le mot <i>rotation</i> vient du latin <i>rotatio</i> avec la même signification et le mot <i>giration</i> vient du latin <i>gyratum</i>, lui-même issu du grec <i>gûros</i> (« cercle »).
</p>
<div class="mw-heading mw-heading2"><h2 id="Exemple_de_la_toupie">Exemple de la toupie</h2></div>
<p>Dans l'exemple du mouvement de la toupie ci-contre, l'angle de nutation <span class="texhtml mvar" style="font-style:italic;">θ</span> mesure l'obliquité de l'axe par rapport à la verticale, l'angle de précession <span class="texhtml mvar" style="font-style:italic;">ψ</span> mesure la rotation de l'axe de la toupie autour de <span class="texhtml mvar" style="font-style:italic;">Oz</span>, et l'angle de rotation propre <span class="texhtml mvar" style="font-style:italic;">φ</span> mesure bien la rotation de la toupie sur elle-même.
</p><p>On voit dans cet exemple que l'angle de précession <span class="texhtml mvar" style="font-style:italic;">ψ</span> est égal à la longitude augmentée d'un angle droit et l'angle de nutation <span class="texhtml mvar" style="font-style:italic;">θ</span> est égal à la colatitude dans les <a href="Coordonn%C3%A9es_sph%C3%A9riques" title="Coordonnées sphériques">coordonnées sphériques</a> de l'axe <span class="texhtml mvar" style="font-style:italic;">Oz'</span> dans <span class="texhtml mvar" style="font-style:italic;">Oxyz</span>.
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<div class="mw-heading mw-heading2"><h2 id="Rotations_d'Euler"><span id="Rotations_d.27Euler"></span>Rotations d'Euler</h2></div>
<div class="mw-heading mw-heading3"><h3 id="Changement_de_référentiel"><span id="Changement_de_r.C3.A9f.C3.A9rentiel"></span>Changement de référentiel</h3></div>
<p>Les trois rotations obtenues en modifiant un des trois angles d'Euler et en gardant les deux autres constants sont la <a href="Pr%C3%A9cession" title="Précession">précession</a>, la <a href="Nutation" title="Nutation">nutation</a> et la rotation propre. On passe du référentiel fixe <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> au référentiel lié au solide <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span> par trois rotations successives :
</p>
<ul><li>La <i><a href="Pr%C3%A9cession" title="Précession">précession</a>,</i> d'angle <span class="texhtml mvar" style="font-style:italic;">ψ</span> autour de l'axe <span class="texhtml mvar" style="font-style:italic;">Oz</span>, qui fait passer de <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> au référentiel <span class="texhtml mvar" style="font-style:italic;">Ouvz</span> (en bleu dans l'image de gauche ci-dessus).</li></ul>
<ul><li>La <i><a href="Nutation" title="Nutation">nutation</a></i>, d'angle <span class="texhtml mvar" style="font-style:italic;">θ</span> autour de l'axe <span class="texhtml mvar" style="font-style:italic;">Ou</span> (ou ligne des nœuds), qui fait passer de <span class="texhtml mvar" style="font-style:italic;">Ouvz</span> à <span class="texhtml mvar" style="font-style:italic;">Ouwz'</span> (en vert).</li></ul>
<ul><li>La <i>rotation propre,</i> ou <i>giration</i>, d'angle <span class="texhtml mvar" style="font-style:italic;">ϕ</span> autour de l'axe <span class="texhtml mvar" style="font-style:italic;">Oz'</span>, qui fait passer de <span class="texhtml mvar" style="font-style:italic;">Ouwz'</span> au référentiel lié au solide <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span> (en rouge).</li></ul>
<p>NB. L'axe <span class="texhtml mvar" style="font-style:italic;">Ou</span> est porté par l'intersection des plans <span class="texhtml mvar" style="font-style:italic;">Oxy</span> et <span class="texhtml mvar" style="font-style:italic;">Ox'y'</span>.
</p><p>Les coordonnées <span class="texhtml">(<i>x'</i>, <i>y'</i>, <i>z'</i>)</span> d'un point dans le référentiel mobile <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span> sont reliées aux coordonnées <span class="texhtml">(<i>x</i>, <i>y</i>, <i>z</i>)</span> de ce même point dans le référentiel fixe <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> par la relation suivante<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> :
</p><p><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\begin{pmatrix}x\\y\\z\end{pmatrix}}_{Oxyz}=A{\begin{pmatrix}x'\\y'\\z'\end{pmatrix}}_{Ox'y'z'}}">
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<mrow class="MJX-TeXAtom-ORD">
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<annotation encoding="application/x-tex">{\displaystyle {\begin{pmatrix}x\\y\\z\end{pmatrix}}_{Oxyz}=A{\begin{pmatrix}x'\\y'\\z'\end{pmatrix}}_{Ox'y'z'}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/0022a9a7865e0412ecc9249f74cf3c15d9fa3119.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.505ex; width:27.448ex; height:9.843ex;" alt="{\displaystyle {\begin{pmatrix}x\\y\\z\end{pmatrix}}_{Oxyz}=A{\begin{pmatrix}x'\\y'\\z'\end{pmatrix}}_{Ox'y'z'}}" loading="lazy"></span> avec la <a href="Matrice_de_passage" class="mw-redirect" title="Matrice de passage">matrice de passage</a> <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A={\begin{pmatrix}\cos \psi \cos \varphi -\sin \psi \cos \theta \sin \varphi &-\cos \psi \sin \varphi -\sin \psi \cos \theta \cos \varphi &\sin \psi \sin \theta \\\sin \psi \cos \varphi +\cos \psi \cos \theta \sin \varphi &-\sin \psi \sin \varphi +\cos \psi \cos \theta \cos \varphi &-\cos \psi \sin \theta \\\sin \theta \sin \varphi &\sin \theta \cos \varphi &\cos \theta \end{pmatrix}}}">
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<annotation encoding="application/x-tex">{\displaystyle A={\begin{pmatrix}\cos \psi \cos \varphi -\sin \psi \cos \theta \sin \varphi &-\cos \psi \sin \varphi -\sin \psi \cos \theta \cos \varphi &\sin \psi \sin \theta \\\sin \psi \cos \varphi +\cos \psi \cos \theta \sin \varphi &-\sin \psi \sin \varphi +\cos \psi \cos \theta \cos \varphi &-\cos \psi \sin \theta \\\sin \theta \sin \varphi &\sin \theta \cos \varphi &\cos \theta \end{pmatrix}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/4e9ca04832d68403adbd4975371db6149e52a2d1.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.171ex; width:84.705ex; height:9.509ex;" alt="{\displaystyle A={\begin{pmatrix}\cos \psi \cos \varphi -\sin \psi \cos \theta \sin \varphi &-\cos \psi \sin \varphi -\sin \psi \cos \theta \cos \varphi &\sin \psi \sin \theta \\\sin \psi \cos \varphi +\cos \psi \cos \theta \sin \varphi &-\sin \psi \sin \varphi +\cos \psi \cos \theta \cos \varphi &-\cos \psi \sin \theta \\\sin \theta \sin \varphi &\sin \theta \cos \varphi &\cos \theta \end{pmatrix}}}" loading="lazy"></span><sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>
</p><p><br>
</p><p>
Rappelons que cette matrice donne aussi verticalement les coordonnées des vecteurs unitaires <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\overrightarrow {x'}},{\overrightarrow {y'}}{\overrightarrow {z'}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<msup>
<mi>x</mi>
<mo>′</mo>
</msup>
<mo>→<!-- → --></mo>
</mover>
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<mo>,</mo>
<mrow class="MJX-TeXAtom-ORD">
<mover>
<msup>
<mi>y</mi>
<mo>′</mo>
</msup>
<mo>→<!-- → --></mo>
</mover>
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<mrow class="MJX-TeXAtom-ORD">
<mover>
<msup>
<mi>z</mi>
<mo>′</mo>
</msup>
<mo>→<!-- → --></mo>
</mover>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\overrightarrow {x'}},{\overrightarrow {y'}}{\overrightarrow {z'}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/95de1e19967bdd93278f217c1aef17d6a47a980d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:8.005ex; height:4.343ex;" alt="{\displaystyle {\overrightarrow {x'}},{\overrightarrow {y'}}{\overrightarrow {z'}}}" loading="lazy"></span> dans la base <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle ({\overrightarrow {x}},{\overrightarrow {y}}{\overrightarrow {z}})}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>x</mi>
<mo>→<!-- → --></mo>
</mover>
</mrow>
<mo>,</mo>
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>y</mi>
<mo>→<!-- → --></mo>
</mover>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>z</mi>
<mo>→<!-- → --></mo>
</mover>
</mrow>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle ({\overrightarrow {x}},{\overrightarrow {y}}{\overrightarrow {z}})}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/57c8eeae92e3e9c2e3972c85d9ab939885acbd17.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:10.153ex; height:3.509ex;" alt="{\displaystyle ({\overrightarrow {x}},{\overrightarrow {y}}{\overrightarrow {z}})}" loading="lazy"></span>.</p><div class="NavFrame" style="border: thin solid #aaaaaa; margin:1em 2em; padding: 0 1em; font-size:100%; text-align:justify; overflow:hidden;">
<div class="NavHead" style="background-color:transparent; color:inherit; padding:0;">Démonstration</div><div class="NavContent" style="padding-bottom:0.4em">
<p>On passe du référentiel <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> au référentiel <span class="texhtml mvar" style="font-style:italic;">Ouvz</span>, par rotation d'angle <span class="texhtml mvar" style="font-style:italic;">ψ</span> autour du troisième axe, donc la matrice de passage est <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B={\begin{pmatrix}\cos \psi &-\sin \psi &0\\\sin \psi &\cos \psi &0\\0&0&1\end{pmatrix}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>B</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow>
<mo>(</mo>
<mtable rowspacing="4pt" columnspacing="1em">
<mtr>
<mtd>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>ψ<!-- ψ --></mi>
</mtd>
<mtd>
<mo>−<!-- − --></mo>
<mi>sin</mi>
<mo><!-- --></mo>
<mi>ψ<!-- ψ --></mi>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mi>sin</mi>
<mo><!-- --></mo>
<mi>ψ<!-- ψ --></mi>
</mtd>
<mtd>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>ψ<!-- ψ --></mi>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
</mtr>
</mtable>
<mo>)</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle B={\begin{pmatrix}\cos \psi &-\sin \psi &0\\\sin \psi &\cos \psi &0\\0&0&1\end{pmatrix}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/df0e58267603fe0dd741a6996de3e3a130b80792.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.171ex; width:27.451ex; height:9.509ex;" alt="{\displaystyle B={\begin{pmatrix}\cos \psi &-\sin \psi &0\\\sin \psi &\cos \psi &0\\0&0&1\end{pmatrix}}}" loading="lazy"></span> .
</p><p>On passe du référentiel <span class="texhtml mvar" style="font-style:italic;">Ouvz</span> au référentiel <span class="texhtml mvar" style="font-style:italic;">Ouwz'</span>, par rotation d'angle <span class="texhtml mvar" style="font-style:italic;">θ</span> autour du premier axe, donc la matrice de passage est <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C={\begin{pmatrix}1&0&0\\0&\cos \theta &-\sin \theta \\0&\sin \theta &\cos \theta \end{pmatrix}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>C</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow>
<mo>(</mo>
<mtable rowspacing="4pt" columnspacing="1em">
<mtr>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>θ<!-- θ --></mi>
</mtd>
<mtd>
<mo>−<!-- − --></mo>
<mi>sin</mi>
<mo><!-- --></mo>
<mi>θ<!-- θ --></mi>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mi>sin</mi>
<mo><!-- --></mo>
<mi>θ<!-- θ --></mi>
</mtd>
<mtd>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>θ<!-- θ --></mi>
</mtd>
</mtr>
</mtable>
<mo>)</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C={\begin{pmatrix}1&0&0\\0&\cos \theta &-\sin \theta \\0&\sin \theta &\cos \theta \end{pmatrix}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/65c686f4661ae2ebba33d069b1e3c28e5b5c78c2.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.005ex; width:26.608ex; height:9.176ex;" alt="{\displaystyle C={\begin{pmatrix}1&0&0\\0&\cos \theta &-\sin \theta \\0&\sin \theta &\cos \theta \end{pmatrix}}}" loading="lazy"></span> .
</p><p>On passe du référentiel <span class="texhtml mvar" style="font-style:italic;">Ouwz'</span> au référentiel <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span>, par rotation d'angle <span class="texhtml mvar" style="font-style:italic;">ϕ</span> autour du troisième axe, donc la matrice de passage est <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D={\begin{pmatrix}\cos \varphi &-\sin \varphi &0\\\sin \varphi &\cos \varphi &0\\0&0&1\end{pmatrix}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>D</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow>
<mo>(</mo>
<mtable rowspacing="4pt" columnspacing="1em">
<mtr>
<mtd>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>φ<!-- φ --></mi>
</mtd>
<mtd>
<mo>−<!-- − --></mo>
<mi>sin</mi>
<mo><!-- --></mo>
<mi>φ<!-- φ --></mi>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mi>sin</mi>
<mo><!-- --></mo>
<mi>φ<!-- φ --></mi>
</mtd>
<mtd>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>φ<!-- φ --></mi>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
</mtr>
</mtable>
<mo>)</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle D={\begin{pmatrix}\cos \varphi &-\sin \varphi &0\\\sin \varphi &\cos \varphi &0\\0&0&1\end{pmatrix}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/e270901873a1486b5baf674a5d22b12813afc42e.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.171ex; width:27.625ex; height:9.509ex;" alt="{\displaystyle D={\begin{pmatrix}\cos \varphi &-\sin \varphi &0\\\sin \varphi &\cos \varphi &0\\0&0&1\end{pmatrix}}}" loading="lazy"></span> .
</p><p>Donc <span class="texhtml mvar" style="font-style:italic;">A = BCD</span> est la matrice de passage du référentiel <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> au référentiel <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span>.
En effectuant le produit des trois matrices on obtient bien le résultat annoncé.
</p>
</div><div class="clear" style="clear:both;"></div>
</div><p>Notons que le passage inverse s'écrit <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\begin{pmatrix}x'\\y'\\z'\end{pmatrix}}_{Ox'y'z'}=A^{T}{\begin{pmatrix}x\\y\\z\end{pmatrix}}_{Oxyz}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mrow class="MJX-TeXAtom-ORD">
<mrow>
<mo>(</mo>
<mtable rowspacing="4pt" columnspacing="1em">
<mtr>
<mtd>
<msup>
<mi>x</mi>
<mo>′</mo>
</msup>
</mtd>
</mtr>
<mtr>
<mtd>
<msup>
<mi>y</mi>
<mo>′</mo>
</msup>
</mtd>
</mtr>
<mtr>
<mtd>
<msup>
<mi>z</mi>
<mo>′</mo>
</msup>
</mtd>
</mtr>
</mtable>
<mo>)</mo>
</mrow>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi>O</mi>
<msup>
<mi>x</mi>
<mo>′</mo>
</msup>
<msup>
<mi>y</mi>
<mo>′</mo>
</msup>
<msup>
<mi>z</mi>
<mo>′</mo>
</msup>
</mrow>
</msub>
<mo>=</mo>
<msup>
<mi>A</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>T</mi>
</mrow>
</msup>
<msub>
<mrow class="MJX-TeXAtom-ORD">
<mrow>
<mo>(</mo>
<mtable rowspacing="4pt" columnspacing="1em">
<mtr>
<mtd>
<mi>x</mi>
</mtd>
</mtr>
<mtr>
<mtd>
<mi>y</mi>
</mtd>
</mtr>
<mtr>
<mtd>
<mi>z</mi>
</mtd>
</mtr>
</mtable>
<mo>)</mo>
</mrow>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mi>O</mi>
<mi>x</mi>
<mi>y</mi>
<mi>z</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\begin{pmatrix}x'\\y'\\z'\end{pmatrix}}_{Ox'y'z'}=A^{T}{\begin{pmatrix}x\\y\\z\end{pmatrix}}_{Oxyz}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/acb11cbf1a25826cfc5c0212e2e25c1ff7cd8da4.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.505ex; width:28.837ex; height:9.843ex;" alt="{\displaystyle {\begin{pmatrix}x'\\y'\\z'\end{pmatrix}}_{Ox'y'z'}=A^{T}{\begin{pmatrix}x\\y\\z\end{pmatrix}}_{Oxyz}}" loading="lazy"></span>, où <span class="texhtml mvar" style="font-style:italic;">A<sup>T</sup></span> est la transposée de <span class="texhtml mvar" style="font-style:italic;">A</span>, cette dernière étant <a href="Matrice_orthogonale" title="Matrice orthogonale">orthogonale</a>.
</p><div class="mw-heading mw-heading3"><h3 id="Interprétation_par_composée_de_rotations"><span id="Interpr.C3.A9tation_par_compos.C3.A9e_de_rotations"></span>Interprétation par composée de rotations</h3></div>
<p>La matrice <span class="texhtml mvar" style="font-style:italic;">A</span> est aussi la matrice dans le référentiel fixe <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> de la rotation <span class="texhtml mvar" style="font-style:italic;">r</span> transformant ce référentiel en <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span>. La décomposition de matrices <span class="texhtml mvar" style="font-style:italic;">A = BCD</span> montre que cette rotation est la composée <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle r=r_{3}\circ r_{2}\circ r_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>r</mi>
<mo>=</mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
<mo>∘<!-- ∘ --></mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>∘<!-- ∘ --></mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle r=r_{3}\circ r_{2}\circ r_{1}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/95efbc78f594eb13964d1bfd3fe1c7d1e2f86fff.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:14.845ex; height:2.009ex;" alt="{\displaystyle r=r_{3}\circ r_{2}\circ r_{1}}" loading="lazy"></span> où
</p>
<ul><li><span class="texhtml"><i>r</i><sub>1</sub></span> est la rotation d'angle <span class="texhtml mvar" style="font-style:italic;">ϕ</span> autour de <span class="texhtml mvar" style="font-style:italic;">Oz</span>,</li>
<li><span class="texhtml"><i>r</i><sub>2</sub></span> est la rotation d'angle <span class="texhtml mvar" style="font-style:italic;">θ</span> autour de <span class="texhtml mvar" style="font-style:italic;">Ox</span>,</li>
<li><span class="texhtml"><i>r</i><sub>3</sub></span> est la rotation d'angle <span class="texhtml mvar" style="font-style:italic;">ψ</span> autour de <span class="texhtml mvar" style="font-style:italic;">Oz</span>.</li></ul>
<div class="mw-heading mw-heading3"><h3 id="Généralité_de_la_décomposition"><span id="G.C3.A9n.C3.A9ralit.C3.A9_de_la_d.C3.A9composition"></span>Généralité de la décomposition</h3></div>
<p>La donnée des deux référentiels <span class="texhtml mvar" style="font-style:italic;">Oxyz</span> et <span class="texhtml mvar" style="font-style:italic;">Ox'y'z'</span> permet de connaitre les angles d'Euler. Celui de nutation <span class="texhtml mvar" style="font-style:italic;">θ</span> est l'angle entre <span class="texhtml mvar" style="font-style:italic;">Oz</span> et <span class="texhtml mvar" style="font-style:italic;">Oz'</span>, l'axe <span class="texhtml mvar" style="font-style:italic;">Ou</span> s'obtient comme perpendiculaire commune à <span class="texhtml mvar" style="font-style:italic;">Oz</span> et <span class="texhtml mvar" style="font-style:italic;">Oz'</span>, et on obtient respectivement <span class="texhtml mvar" style="font-style:italic;">ψ</span> et <span class="texhtml mvar" style="font-style:italic;">ϕ</span> comme angles entre <span class="texhtml mvar" style="font-style:italic;">Ox</span> et <span class="texhtml mvar" style="font-style:italic;">Ou</span> et entre <span class="texhtml mvar" style="font-style:italic;">Ou</span> et <span class="texhtml mvar" style="font-style:italic;">Ox'</span>.
</p><p>La matrice <span class="texhtml mvar" style="font-style:italic;">A</span> ci-dessus est donc la matrice générale d'une rotation, et la décomposition <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle r=r_{3}\circ r_{2}\circ r_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>r</mi>
<mo>=</mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
<mo>∘<!-- ∘ --></mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>∘<!-- ∘ --></mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle r=r_{3}\circ r_{2}\circ r_{1}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/95efbc78f594eb13964d1bfd3fe1c7d1e2f86fff.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:14.845ex; height:2.009ex;" alt="{\displaystyle r=r_{3}\circ r_{2}\circ r_{1}}" loading="lazy"></span> prouve que le groupe des rotations d'axe passant par <i>O</i> est engendré par les rotations d'axes l'un de deux axes orthogonaux donnés passant par <i>O</i>.
</p><p>En terme d'aéronautique, cela signifie qu'on obtient l'orientation quelconque d'un avion en utilisant deux des trois rotations : <a href="Roulis" title="Roulis">roulis</a> (d'axe la carlingue), <a href="Tangage" title="Tangage">tangage</a> (d'axe les ailes), et <a href="Lacet_(mouvement)" title="Lacet (mouvement)">lacet</a> (d'axe la verticale), par exemple roulis puis tangage puis roulis.
</p><p>Autre conséquence : lorsqu'on manipule à la souris un objet visualisé à l'écran (vers le haut : rotation autour de l'horizontale, vers la droite : rotation autour de la verticale), on obtient toutes les orientations possibles de l'objet.
</p><p>Nota : <span class="texhtml mvar" style="font-style:italic;">r</span> est la rotation d'angle <span class="texhtml">α</span> autour de <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\overrightarrow {n}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>n</mi>
<mo>→<!-- → --></mo>
</mover>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\overrightarrow {n}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/589d8abc2a0543f71bed700b758615e5fea08c06.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.324ex; height:3.009ex;" alt="{\displaystyle {\overrightarrow {n}}}" loading="lazy"></span> où
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \cos \alpha =\cos ^{2}\left({\frac {\varphi +\psi }{2}}\right)\cos \theta -\sin ^{2}\left({\frac {\varphi +\psi }{2}}\right),\,\cos {\frac {\alpha }{2}}=\cos {\frac {\theta }{2}}\cos {\frac {\varphi +\psi }{2}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>cos</mi>
<mo><!-- --></mo>
<mi>α<!-- α --></mi>
<mo>=</mo>
<msup>
<mi>cos</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>φ<!-- φ --></mi>
<mo>+</mo>
<mi>ψ<!-- ψ --></mi>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mi>cos</mi>
<mo><!-- --></mo>
<mi>θ<!-- θ --></mi>
<mo>−<!-- − --></mo>
<msup>
<mi>sin</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msup>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>φ<!-- φ --></mi>
<mo>+</mo>
<mi>ψ<!-- ψ --></mi>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>cos</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>α<!-- α --></mi>
<mn>2</mn>
</mfrac>
</mrow>
<mo>=</mo>
<mi>cos</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>θ<!-- θ --></mi>
<mn>2</mn>
</mfrac>
</mrow>
<mi>cos</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>φ<!-- φ --></mi>
<mo>+</mo>
<mi>ψ<!-- ψ --></mi>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \cos \alpha =\cos ^{2}\left({\frac {\varphi +\psi }{2}}\right)\cos \theta -\sin ^{2}\left({\frac {\varphi +\psi }{2}}\right),\,\cos {\frac {\alpha }{2}}=\cos {\frac {\theta }{2}}\cos {\frac {\varphi +\psi }{2}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/4c2d306aeb59e732b11c85eb649cb3bb5222b22c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:70.671ex; height:6.176ex;" alt="{\displaystyle \cos \alpha =\cos ^{2}\left({\frac {\varphi +\psi }{2}}\right)\cos \theta -\sin ^{2}\left({\frac {\varphi +\psi }{2}}\right),\,\cos {\frac {\alpha }{2}}=\cos {\frac {\theta }{2}}\cos {\frac {\varphi +\psi }{2}}}" loading="lazy"></span>,</dd></dl>
<p>et <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \sin {\frac {\alpha }{2}}{\overrightarrow {n}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>sin</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>α<!-- α --></mi>
<mn>2</mn>
</mfrac>
</mrow>
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>n</mi>
<mo>→<!-- → --></mo>
</mover>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \sin {\frac {\alpha }{2}}{\overrightarrow {n}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/599dd53373eb9bd5104c34df8678341af763d249.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:7.89ex; height:4.676ex;" alt="{\displaystyle \sin {\frac {\alpha }{2}}{\overrightarrow {n}}}" loading="lazy"></span> a pour coordonnées <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \left(\cos \left({\frac {\psi -\varphi }{2}}\right)\sin {\frac {\theta }{2}},\sin \left({\frac {\psi -\varphi }{2}}\right)\sin {\frac {\theta }{2}},\sin \left({\frac {\psi +\varphi }{2}}\right)\cos {\frac {\theta }{2}}\right)}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow>
<mo>(</mo>
<mrow>
<mi>cos</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>ψ<!-- ψ --></mi>
<mo>−<!-- − --></mo>
<mi>φ<!-- φ --></mi>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mi>sin</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>θ<!-- θ --></mi>
<mn>2</mn>
</mfrac>
</mrow>
<mo>,</mo>
<mi>sin</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>ψ<!-- ψ --></mi>
<mo>−<!-- − --></mo>
<mi>φ<!-- φ --></mi>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mi>sin</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>θ<!-- θ --></mi>
<mn>2</mn>
</mfrac>
</mrow>
<mo>,</mo>
<mi>sin</mi>
<mo><!-- --></mo>
<mrow>
<mo>(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mrow>
<mi>ψ<!-- ψ --></mi>
<mo>+</mo>
<mi>φ<!-- φ --></mi>
</mrow>
<mn>2</mn>
</mfrac>
</mrow>
<mo>)</mo>
</mrow>
<mi>cos</mi>
<mo><!-- --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>θ<!-- θ --></mi>
<mn>2</mn>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \left(\cos \left({\frac {\psi -\varphi }{2}}\right)\sin {\frac {\theta }{2}},\sin \left({\frac {\psi -\varphi }{2}}\right)\sin {\frac {\theta }{2}},\sin \left({\frac {\psi +\varphi }{2}}\right)\cos {\frac {\theta }{2}}\right)}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/95930c557f65da49a8b9db421bef0a0162f4e10d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:61.845ex; height:6.176ex;" alt="{\displaystyle \left(\cos \left({\frac {\psi -\varphi }{2}}\right)\sin {\frac {\theta }{2}},\sin \left({\frac {\psi -\varphi }{2}}\right)\sin {\frac {\theta }{2}},\sin \left({\frac {\psi +\varphi }{2}}\right)\cos {\frac {\theta }{2}}\right)}" loading="lazy"></span>.
</p><p>On obtient la première relation en écrivant que la trace de <span class="texhtml mvar" style="font-style:italic;">A</span> est égale à <span class="texhtml">1 + 2 cos α</span>.
</p><p>La deuxième et la troisième deuxième s'obtiennent facilement en écrivant les <a href="Formule_d'Euler%E2%80%93Rodrigues" title="Formule d'Euler–Rodrigues">matrices d'Euler-Rodrigues</a> de <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle r_{3},r_{2},r_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>,</mo>
<msub>
<mi>r</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle r_{3},r_{2},r_{1}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c2610013d35c2119ed9a8adb689feaea22984096.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:8.377ex; height:2.009ex;" alt="{\displaystyle r_{3},r_{2},r_{1}}" loading="lazy"></span> et en effectuant leur produit.
</p><p>Exemple : la rotation d'un tiers de tour autour de <span class="texhtml">(1 , 1 , 1)</span> de matrice <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A={\begin{pmatrix}0&0&1\\1&0&0\\0&1&0\end{pmatrix}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>A</mi>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow>
<mo>(</mo>
<mtable rowspacing="4pt" columnspacing="1em">
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
<mtr>
<mtd>
<mn>0</mn>
</mtd>
<mtd>
<mn>1</mn>
</mtd>
<mtd>
<mn>0</mn>
</mtd>
</mtr>
</mtable>
<mo>)</mo>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle A={\begin{pmatrix}0&0&1\\1&0&0\\0&1&0\end{pmatrix}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/13a4467823162f788cd1057a5d11e394a4087e6c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.005ex; width:17.792ex; height:9.176ex;" alt="{\displaystyle A={\begin{pmatrix}0&0&1\\1&0&0\\0&1&0\end{pmatrix}}}" loading="lazy"></span> a pour angles d'Euler <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle (\varphi ,\theta ,\psi )=\left(\pi ,-{\pi \over 2},-{\pi \over 2}\right)}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
<mi>φ<!-- φ --></mi>
<mo>,</mo>
<mi>θ<!-- θ --></mi>
<mo>,</mo>
<mi>ψ<!-- ψ --></mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mrow>
<mo>(</mo>
<mrow>
<mi>π<!-- π --></mi>
<mo>,</mo>
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>π<!-- π --></mi>
<mn>2</mn>
</mfrac>
</mrow>
<mo>,</mo>
<mo>−<!-- − --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mfrac>
<mi>π<!-- π --></mi>
<mn>2</mn>
</mfrac>
</mrow>
</mrow>
<mo>)</mo>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle (\varphi ,\theta ,\psi )=\left(\pi ,-{\pi \over 2},-{\pi \over 2}\right)}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c1c0e5dbb5c46c6aa03930cd734587d5eaf10f83.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:25.227ex; height:4.843ex;" alt="{\displaystyle (\varphi ,\theta ,\psi )=\left(\pi ,-{\pi \over 2},-{\pi \over 2}\right)}" loading="lazy"></span>.
</p>
<div class="mw-heading mw-heading2"><h2 id="Mécanique_du_solide"><span id="M.C3.A9canique_du_solide"></span>Mécanique du solide</h2></div>
<p>On s'intéresse seulement ici à la description du mouvement du solide en rotation quelconque autour du point O, qui peut être un point fixe du solide dans le référentiel de référence <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Oxyz}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>O</mi>
<mi>x</mi>
<mi>y</mi>
<mi>z</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle Oxyz}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/be27c2ad2be5d640cfc2a530df87d9b7b4ebf615.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:5.347ex; height:2.509ex;" alt="{\displaystyle Oxyz}" loading="lazy"></span> ou le centre de masse. Les angles d'Euler sont choisis de façon à permettre une mémorisation simple de la construction du vecteur rotation instantané du solide, nécessaire à l'étude de la <a href="Cin%C3%A9matique_du_solide" class="mw-redirect" title="Cinématique du solide">cinématique du solide</a>. Le vecteur rotation instantané du solide est en effet donné par la simple somme :
</p>
<dl><dd><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\vec {\Omega }}={\dot {\psi }}\,{\vec {z}}+{\dot {\theta }}\,{\vec {u}}+{\dot {\varphi }}\,{\vec {z'}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi mathvariant="normal">Ω<!-- Ω --></mi>
<mo stretchy="false">→<!-- → --></mo>
</mover>
</mrow>
</mrow>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>ψ<!-- ψ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>z</mi>
<mo stretchy="false">→<!-- → --></mo>
</mover>
</mrow>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>θ<!-- θ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>u</mi>
<mo stretchy="false">→<!-- → --></mo>
</mover>
</mrow>
</mrow>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>φ<!-- φ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<msup>
<mi>z</mi>
<mo>′</mo>
</msup>
<mo stretchy="false">→<!-- → --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\vec {\Omega }}={\dot {\psi }}\,{\vec {z}}+{\dot {\theta }}\,{\vec {u}}+{\dot {\varphi }}\,{\vec {z'}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/be028eda4c4801b72a38e9ce6efd6c2b1d980261.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:20.986ex; height:4.509ex;" alt="{\displaystyle {\vec {\Omega }}={\dot {\psi }}\,{\vec {z}}+{\dot {\theta }}\,{\vec {u}}+{\dot {\varphi }}\,{\vec {z'}}}" loading="lazy"></span>,</dd></dl>
<p>où les vecteurs apparaissant dans le membre de droite sont les vecteurs unitaires des axes correspondants et les expressions <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\dot {\psi }},\,{\dot {\theta }},\,{\dot {\varphi }}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>ψ<!-- ψ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>θ<!-- θ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>φ<!-- φ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\dot {\psi }},\,{\dot {\theta }},\,{\dot {\varphi }}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/055b4d38b096ad2ab64754f86203ef5bdf7a1865.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:7.328ex; height:3.343ex;" alt="{\displaystyle {\dot {\psi }},\,{\dot {\theta }},\,{\dot {\varphi }}}" loading="lazy"></span> sont respectivement les <a href="Vitesse_angulaire" title="Vitesse angulaire">vitesses angulaires</a> de précession, de nutation et de rotation propre. On remarquera que l'expression simple précédente utilise une base non orthogonale.
</p><p>L'utilisation des angles d'Euler est très générale en mécanique et en astronomie, par exemple pour décrire le mouvement du <a href="Gyroscope" title="Gyroscope">gyroscope</a> : dans l'animation ci-contre, les vitesses de précession <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\dot {\psi }}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>ψ<!-- ψ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\dot {\psi }}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/7c6912355df049856322d8d4d631156fa10f3a37.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.596ex; height:3.009ex;" alt="{\displaystyle {\dot {\psi }}}" loading="lazy"></span> et de rotation propre <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\dot {\varphi }}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>φ<!-- φ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\dot {\varphi }}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/92ffa1fdb663e8557bd7ebb66a095b54ba9f57e5.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:1.535ex; height:2.676ex;" alt="{\displaystyle {\dot {\varphi }}}" loading="lazy"></span> sont constantes et la vitesse de nutation <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\dot {\theta }}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>θ<!-- θ --></mi>
<mo>˙<!-- ˙ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\dot {\theta }}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/f78124b2aea53527d3e053cbbdd9c7ded2c8f05f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.356ex; height:2.843ex;" alt="{\displaystyle {\dot {\theta }}}" loading="lazy"></span> est nulle, l'angle de nutation restant constant.
</p>
<div class="mw-heading mw-heading2"><h2 id="Orientation_cristalline">Orientation cristalline</h2></div>
<p>En <a href="Science_des_mat%C3%A9riaux" title="Science des matériaux">science des matériaux</a>, les angles d'Euler sont utilisés pour décrire l'<a href="Orientation_cristalline" title="Orientation cristalline">orientation cristalline</a> (orientation d'un <a href="Cristallite" title="Cristallite">cristallite</a> par rapport aux axes de l'échantillon), notamment dans le domaine de la <a href="Texture" class="mw-disambig" title="Texture">texture</a> (orientation préférentielle). Les angles sont alors en général<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> notés (<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varphi _{1},\Phi ,\varphi _{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>φ<!-- φ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<mi mathvariant="normal">Φ<!-- Φ --></mi>
<mo>,</mo>
<msub>
<mi>φ<!-- φ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \varphi _{1},\Phi ,\varphi _{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/5e2549abc1fe8a806b09d710e7b611addc9a2c15.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:8.895ex; height:2.676ex;" alt="{\displaystyle \varphi _{1},\Phi ,\varphi _{2}}" loading="lazy"></span>) avec :
</p>
<ul><li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varphi _{1}=\psi }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>φ<!-- φ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>=</mo>
<mi>ψ<!-- ψ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \varphi _{1}=\psi }</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/8dae73481c0ceb7b88549749358f5bb95a2413be.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:7.186ex; height:2.676ex;" alt="{\displaystyle \varphi _{1}=\psi }" loading="lazy"></span> ;</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Phi =\theta }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Φ<!-- Φ --></mi>
<mo>=</mo>
<mi>θ<!-- θ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \Phi =\theta }</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/a2ecc5ea0000cf6a557a2261c13b29370c247344.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:5.867ex; height:2.176ex;" alt="{\displaystyle \Phi =\theta }" loading="lazy"></span> ;</li>
<li><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varphi _{2}=\varphi }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>φ<!-- φ --></mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mo>=</mo>
<mi>φ<!-- φ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \varphi _{2}=\varphi }</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/9ed87f06fa344221d70d9a8a16cf53cfc346db80.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:7.193ex; height:2.176ex;" alt="{\displaystyle \varphi _{2}=\varphi }" loading="lazy"></span>.</li></ul>
<p>On utilise parfois une autre variante dans laquelle la seconde rotation (<a href="Nutation" title="Nutation">nutation</a>) se fait selon l'axe <span class="texhtml">O<i>v</i></span> au lieu de <span class="texhtml">O<i>u</i></span> ; les angles sont alors notés (<span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Phi ,\Theta ,\Psi }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi mathvariant="normal">Φ<!-- Φ --></mi>
<mo>,</mo>
<mi mathvariant="normal">Θ<!-- Θ --></mi>
<mo>,</mo>
<mi mathvariant="normal">Ψ<!-- Ψ --></mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \Phi ,\Theta ,\Psi }</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/671a205fb03e77437471c137b80fcd2909b7cbef.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:7.362ex; height:2.509ex;" alt="{\displaystyle \Phi ,\Theta ,\Psi }" loading="lazy"></span>) sans que cela ait un rapport avec les notations des mécaniciens, ce qui n'est pas sans risque de confusion.
</p><p><span typeof="mw:File"></span>
</p>
<div class="mw-heading mw-heading2"><h2 id="Notes_et_références"><span id="Notes_et_r.C3.A9f.C3.A9rences"></span>Notes et références</h2></div>
<div class="references-small decimal" style=""><div class="mw-references-wrap"><ol class="references">
<li id="cite_note-TailletVillainFebvre201830''<abbr_class="abbr_"_title="sub_verbo_(«_à_l'article_»)"_>s.v.</abbr>''angles_d'Euler-1"><span class="reference-text"><a href="#TailletVillainFebvre2018">Taillet, Villain et Febvre 2018</a>, <i><abbr class="abbr" title="sub verbo (« à l'article »)">s.v.</abbr></i>angles d'Euler, <abbr class="abbr" title="page(s)">p.</abbr> 30. </span>
</li>
<li id="cite_note-Pérez2014<abbr_class="abbr_"_title="21"_><span_class="romain"_style="text-transform:lowercase;_font-variant:normal;">xxi</span></abbr>_et_275-2"><span class="mw-cite-backlink"><a href="#cite_ref-Pérez2014<abbr_class="abbr_"_title="21"_><span_class="romain"_style="text-transform:lowercase;_font-variant:normal;">xxi</span></abbr>_et_275_2-0">↑</a> </span><span class="reference-text"><a href="#Pérez2014">Pérez 2014</a>, <abbr class="abbr" title="page(s)">p.</abbr> <abbr class="abbr" title="21"><span class="romain" style="text-transform:lowercase; font-variant:normal;">xxi</span></abbr> et 275. </span>
</li>
<li id="cite_note-3"><span class="mw-cite-backlink"><a href="#cite_ref-3">↑</a> </span><span class="reference-text"><span class="ouvrage">« <a class="external text" href="https://fr.wiktionary.org/wiki/nutation"><cite style="font-style:normal;">Nutation</cite></a> », sur <span class="italique">Wiktionnaire</span></span></span>
</li>
<li id="cite_note-4"><span class="mw-cite-backlink"><a href="#cite_ref-4">↑</a> </span><span class="reference-text"><span class="ouvrage">« <a rel="nofollow" class="external text" href="http://ressources.univ-lemans.fr/AccesLibre/UM/Pedago/physique/02/meca/angleeuler.html"><cite style="font-style:normal;">Les angles d'Euler</cite></a> », sur <span class="italique">Physique et simulations numériques, Faculté des Sciences exactes et naturelles, Université du Maine</span></span></span>
</li>
<li id="cite_note-5"><span class="mw-cite-backlink"><a href="#cite_ref-5">↑</a> </span><span class="reference-text"><span class="ouvrage" id="Euler1770"><span class="ouvrage" id="Leonhard_Euler1770"><abbr class="abbr indicateur-langue" title="Langue : latin">(la)</abbr> Leonhard Euler, « <cite style="font-style:normal" lang="la">Problema algebraicum ob affectiones prorsus singulares memorabile</cite> », <i><span class="lang-la" lang="la">Commentatio 407 Indicis Enestoemiani, Novi Comm. Acad. Sci. Petropolitanae 15</span></i>, <time>1770</time>, la "matrice" se trouve page 83 <small style="line-height:1em;">(<a rel="nofollow" class="external text" href="https://scholarlycommons.pacific.edu/cgi/viewcontent.cgi?article=1406&context=euler-works">lire en ligne</a>)</small><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Problema+algebraicum+ob+affectiones+prorsus+singulares+memorabile&rft.jtitle=Commentatio+407+Indicis+Enestoemiani%2C+Novi+Comm.+Acad.+Sci.+Petropolitanae+15&rft.aulast=Euler&rft.aufirst=Leonhard&rft.date=1770&rft.pages=la+%22matrice%22+se+trouve+page+83&rfr_id=info%3Asid%2Ffr.wikipedia.org%3AAngles+d%27Euler"></span></span></span></span>
</li>
<li id="cite_note-Liss2-6"><span class="mw-cite-backlink"><a href="#cite_ref-Liss2_6-0">↑</a> </span><span class="reference-text"><span class="ouvrage" id="KD,_Bartels_A,_Schreyer_A,_Clemens_H2003"><span class="ouvrage" id="Liss_KD,_Bartels_A,_Schreyer_A,_Clemens_H2003">Liss KD, Bartels A, Schreyer A, Clemens H, « <cite style="font-style:normal">High energy X-rays: A tool for advanced bulk investigations in materials science and physics</cite> », <i>Textures Microstruct.</i>, <abbr class="abbr" title="volume">vol.</abbr> 35, <abbr class="abbr" title="numéros">n<sup>os</sup></abbr> 3/4, <time>2003</time>, <abbr class="abbr" title="pages">p.</abbr> <span class="nowrap">219–52</span> <small style="line-height:1em;">(<a href="Digital_Object_Identifier" title="Digital Object Identifier">DOI</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://dx.doi.org/10.1080/07303300310001634952">10.1080/07303300310001634952</a></span>)</small><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=High+energy+X-rays%3A+A+tool+for+advanced+bulk+investigations+in+materials+science+and+physics&rft.jtitle=Textures+Microstruct.&rft.issue=3%2F4&rft.au=Liss+KD%2C+Bartels+A%2C+Schreyer+A%2C+Clemens+H&rft.date=2003&rft.volume=35&rft.pages=219%E2%80%9352&rft_id=info%3Adoi%2F10.1080%2F07303300310001634952&rfr_id=info%3Asid%2Ffr.wikipedia.org%3AAngles+d%27Euler"></span></span></span></span>
</li>
<li id="cite_note-7"><span class="mw-cite-backlink"><a href="#cite_ref-7">↑</a> </span><span class="reference-text">il s'agit de la notation adoptée par Bunge dans son ouvrage <i>Texture analysis in materials science</i>, une référence dans le domaine</span>
</li>
</ol></div>
</div>
<div class="mw-heading mw-heading2"><h2 id="Voir_aussi">Voir aussi</h2></div>
<div class="mw-heading mw-heading3"><h3 id="Bibliographie">Bibliographie</h3></div>
<ul><li><span class="ouvrage" id="Lehning2007"><span class="ouvrage" id="H._Lehning2007"><small>[Lehning 2007]</small> <a href="Herv%C3%A9_Lehning" title="Hervé Lehning"><abbr class="abbr" title="Hervé">H.</abbr> <span class="nom_auteur">Lehning</span></a>, <cite style="font-style:normal">« Les angles d'Euler »</cite>, dans <span class="nowrap"><abbr class="abbr" title="Hervé">H.</abbr> Lehning</span> (<abbr class="abbr" title="sous la direction de">dir.</abbr>), <cite class="italique">Leonhard Euler : un génie des Lumières</cite>, Paris, Pôle, <abbr class="abbr" title="collection">coll.</abbr> « <abbr class="abbr" title="Bibliothèque">Biblioth.</abbr> Tangente » (<abbr class="abbr" title="numéro">n<sup>o</sup></abbr> 29), <time class="nowrap" datetime="2007-05" data-sort-value="2007-05">mai 2007</time>, <abbr class="abbr" title="première">1<sup>re</sup></abbr> <abbr class="abbr" title="édition">éd.</abbr>, 1 <abbr class="abbr" title="vol."><abbr class="abbr" title="volume(s)">vol.</abbr></abbr>, 154, <abbr class="abbr" title="illustration(s)">ill.</abbr> et <abbr class="abbr" title="portrait(s)">portr.</abbr>, 17 × 24 <abbr class="abbr" title="centimètre">cm</abbr> <small style="line-height:1em;">(<a href="International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <span class="nowrap">978-2-8488-4066-6</span>, <a href="EAN_13" title="EAN 13">EAN</a> <span class="nowrap">9782848840666</span>, <a href="Online_Computer_Library_Center" title="Online Computer Library Center">OCLC</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://worldcat.org/fr/title/470945066">470945066</a></span>, <a href="Biblioth%C3%A8que_nationale_de_France" title="Bibliothèque nationale de France">BNF</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://catalogue.bnf.fr/ark:/12148/cb41041045n.public">41041045</a></span>, <a href="Syst%C3%A8me_universitaire_de_documentation" title="Système universitaire de documentation">SUDOC</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://www.sudoc.fr/11449309X">11449309X</a></span>)</small>, dossier <abbr class="abbr" title="numéro">n<sup>o</sup></abbr> 2, <abbr class="abbr" title="article(s)">art.</abbr> <abbr class="abbr" title="numéro">n<sup>o</sup></abbr> 8, <abbr class="abbr" title="pages">p.</abbr> <span class="nowrap">64-65</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Leonhard+Euler&rft.atitle=Les+angles+d%27Euler&rft.place=Paris&rft.pub=P%C3%B4le&rft.edition=1&rft.stitle=un+g%C3%A9nie+des+Lumi%C3%A8res&rft.aulast=Lehning&rft.aufirst=%3Cabbr+class%3D%22abbr+%22+title%3D%22Herv%C3%A9%22+%3EH.%3C%2Fabbr%3E&rft.date=2007-05&rft.pages=64-65&rft.tpages=1%C2%A0%3Cabbr+class%3D%22abbr%22+title%3D%22vol.%22%3E%3Cabbr+class%3D%22abbr+%22+title%3D%22volume%28s%29%22+%3Evol.%3C%2Fabbr%3E%3C%2Fabbr%3E%2C+154&rft_id=info%3Aoclcnum%2F470945066&rfr_id=info%3Asid%2Ffr.wikipedia.org%3AAngles+d%27Euler"></span></span></span>.</li>
<li><span class="ouvrage" id="Pérez2014"><span class="ouvrage" id="José-Philippe_Pérez2014"><small>[Pérez 2014]</small> José-Philippe <span class="nom_auteur">Pérez</span> (avec la collaboration d'Olivier Pujol), <cite class="italique">Mécanique : fondements et applications</cite>, Paris, <a href="%C3%89ditions_Dunod" title="Éditions Dunod">Dunod</a>, hors <abbr class="abbr" title="collection">coll.</abbr>, <time class="nowrap" datetime="2014-09" data-sort-value="2014-09">septembre 2014</time>, <abbr class="abbr" title="septième">7<sup>e</sup></abbr> <abbr class="abbr" title="édition">éd.</abbr> (<abbr class="abbr" title="première">1<sup>re</sup></abbr> <abbr class="abbr" title="édition">éd.</abbr> <time>1984</time>), <span class="nowrap">1 vol.</span>, <abbr class="abbr" title="26"><span class="romain" style="text-transform:uppercase">XXVI</span></abbr>-801, 17,5 × 24 <abbr class="abbr" title="centimètre">cm</abbr> <small style="line-height:1em;">(<a href="International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <span class="nowrap">978-2-10-071232-8</span>, <a href="EAN_13" title="EAN 13">EAN</a> <span class="nowrap">9782100712328</span>, <a href="Online_Computer_Library_Center" title="Online Computer Library Center">OCLC</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://worldcat.org/fr/title/892897104">892897104</a></span>, <a href="Biblioth%C3%A8que_nationale_de_France" title="Bibliothèque nationale de France">BNF</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://catalogue.bnf.fr/ark:/12148/cb43887529q.public">43887529</a></span>, <a href="Syst%C3%A8me_universitaire_de_documentation" title="Système universitaire de documentation">SUDOC</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://www.sudoc.fr/180751727">180751727</a></span>, <a rel="nofollow" class="external text" href="https://www.dunod.com/sciences-techniques/mecanique-fondements-et-applications-avec-320-exercices-et-problemes-resolus">présentation en ligne</a>, <a rel="nofollow" class="external text" href="https://books.google.com/books?id=9tB8BAAAQBAJ">lire en ligne</a>)</small><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=M%C3%A9canique&rft.place=Paris&rft.pub=Dunod&rft.edition=7&rft.stitle=fondements+et+applications&rft.aulast=P%C3%A9rez&rft.aufirst=Jos%C3%A9-Philippe&rft.date=2014-09&rft.tpages=%3Cspan+class%3D%22nowrap%22%3E1+vol.%3C%2Fspan%3E%2C+%3Cabbr+class%3D%22abbr+%22+title%3D%2226%22+%3E%3Cspan+class%3D%22romain%22+style%3D%22text-transform%3Auppercase%22%3EXXVI%3C%2Fspan%3E%3C%2Fabbr%3E-801&rft.isbn=978-2-10-071232-8&rft_id=info%3Aoclcnum%2F892897104&rfr_id=info%3Asid%2Ffr.wikipedia.org%3AAngles+d%27Euler"></span></span></span>.</li>
<li><span class="ouvrage" id="TailletVillainFebvre2018"><span class="ouvrage" id="R._TailletL._VillainP._Febvre2018"><small>[Taillet, Villain et Febvre 2018]</small> <abbr class="abbr" title="Richard">R.</abbr> <span class="nom_auteur">Taillet</span>, <abbr class="abbr" title="Loïc">L.</abbr> <span class="nom_auteur">Villain</span> et <abbr class="abbr" title="Pascal">P.</abbr> <span class="nom_auteur">Febvre</span>, <cite class="italique">Dictionnaire de physique</cite>, Louvain-la-Neuve, <a href="De_Boeck_Sup%C3%A9rieur" class="mw-redirect" title="De Boeck Supérieur">De Boeck Sup.</a>, hors <abbr class="abbr" title="collection">coll.</abbr>, <time class="nowrap" datetime="2018"><abbr class="abbr" title="janvier">janv.</abbr> 2018</time>, <abbr class="abbr" title="quatrième">4<sup>e</sup></abbr> <abbr class="abbr" title="édition">éd.</abbr> (<abbr class="abbr" title="première">1<sup>re</sup></abbr> <abbr class="abbr" title="édition">éd.</abbr> <time class="nowrap" datetime="2008-05" data-sort-value="2008-05">mai 2008</time>), 1 <abbr class="abbr" title="vol."><abbr class="abbr" title="volume(s)">vol.</abbr></abbr>, <abbr class="abbr" title="10"><span class="romain" style="text-transform:uppercase">X</span></abbr>-956, <abbr class="abbr" title="illustration(s)">ill.</abbr> et <abbr class="abbr" title="figure(s)">fig.</abbr>, 24 <abbr class="abbr" title="centimètre">cm</abbr> <small style="line-height:1em;">(<a href="International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <span class="nowrap">978-2-8073-0744-5</span>, <a href="EAN_13" title="EAN 13">EAN</a> <span class="nowrap">9782807307445</span>, <a href="Online_Computer_Library_Center" title="Online Computer Library Center">OCLC</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://worldcat.org/fr/title/1022951339">1022951339</a></span>, <a href="Syst%C3%A8me_universitaire_de_documentation" title="Système universitaire de documentation">SUDOC</a> <span class=" noarchive nowrap"><a rel="nofollow" class="external text" href="https://www.sudoc.fr/224228161">224228161</a></span>, <a rel="nofollow" class="external text" href="https://www.deboecksuperieur.com/ouvrage/9782807307445-dictionnaire-de-physique">présentation en ligne</a>, <a rel="nofollow" class="external text" href="https://books.google.com/books?id=pjlFDwAAQBAJ">lire en ligne</a>)</small>, <i><abbr class="abbr" title="sub verbo (« à l'article »)">s.v.</abbr></i>angles d'Euler, <abbr class="abbr" title="page(s)">p.</abbr> 30, <span class="nowrap"><abbr class="abbr" title="colonne(s)">col.</abbr> 1-2</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Dictionnaire+de+physique&rft.place=Louvain-la-Neuve&rft.pub=De+Boeck+Sup.&rft.edition=4&rft.aulast=Taillet&rft.aufirst=%3Cabbr+class%3D%22abbr+%22+title%3D%22Richard%22+%3ER.%3C%2Fabbr%3E&rft.au=Villain%2C+%3Cabbr+class%3D%22abbr+%22+title%3D%22Lo%C3%AFc%22+%3EL.%3C%2Fabbr%3E&rft.au=Febvre%2C+%3Cabbr+class%3D%22abbr+%22+title%3D%22Pascal%22+%3EP.%3C%2Fabbr%3E&rft.date=2018&rft.pages=30%2C+%3Cspan+class%3D%22nowrap%22%3E%3Cabbr+class%3D%22abbr+%22+title%3D%22colonne%28s%29%22+%3Ecol.%3C%2Fabbr%3E%26nbsp%3B1-2%3C%2Fspan%3E&rft.tpages=1%C2%A0%3Cabbr+class%3D%22abbr%22+title%3D%22vol.%22%3E%3Cabbr+class%3D%22abbr+%22+title%3D%22volume%28s%29%22+%3Evol.%3C%2Fabbr%3E%3C%2Fabbr%3E%2C+%3Cabbr+class%3D%22abbr+%22+title%3D%2210%22+%3E%3Cspan+class%3D%22romain%22+style%3D%22text-transform%3Auppercase%22%3EX%3C%2Fspan%3E%3C%2Fabbr%3E-956&rft_id=info%3Aoclcnum%2F1022951339&rfr_id=info%3Asid%2Ffr.wikipedia.org%3AAngles+d%27Euler"></span></span></span>.</li></ul>
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<div class="mw-heading mw-heading3"><h3 id="Liens_externes">Liens externes</h3></div>
<ul><li><a rel="nofollow" class="external text" href="https://phyanim.sciences.univ-nantes.fr/Meca/Cinematique/euler1.php">Une animation des angles d'Euler</a></li></ul>
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