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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Isometrie</span></h1>
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<p>Eine <b>Isometrie</b> (<span style="font-style:normal;font-weight:normal"><a href="Neugriechische_Sprache" title="Neugriechische Sprache">griechisch</a></span> <span lang="el-Grek" class="Grek" style="font-style:normal">Ισομετρία</span> Isometría: gleiches Maß, Längengleichheit, Längentreue<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>) ist in der <a href="Mathematik" title="Mathematik">Mathematik</a> eine <a href="Funktion_(Mathematik)" title="Funktion (Mathematik)">Abbildung</a>, die zwei <a href="Metrischer_Raum" title="Metrischer Raum">metrische Räume</a> aufeinander abbildet und dabei die Metrik (Abstand, Distanz) erhält. Das heißt, der Abstand zweier Bildpunkte ist gleich groß wie der der Urbildpunkte.
</p><p>In der <a href="Euklidische_Geometrie" title="Euklidische Geometrie">euklidischen</a> und der <a href="Synthetische_Geometrie" title="Synthetische Geometrie">synthetischen Geometrie</a> werden speziell solche Isometrien betrachtet, die zugleich <a href="Abbildungsgeometrie" title="Abbildungsgeometrie">geometrische Abbildungen</a> für die betrachteten Räume sind. Meist spricht man dann von einer <b>abstandserhaltenden</b>, <b>längentreuen</b> oder auch <b>isometrischen</b> Abbildung, und wenn die geforderten Zusatzeigenschaften aus dem Zusammenhang klar sind, einfach von einer <i>Isometrie</i>.
</p><p>Davon abweichend versteht man in der <a href="Riemannsche_Geometrie" title="Riemannsche Geometrie">riemannschen Geometrie</a> unter einer <i><a href="Isometrie_(Riemannsche_Geometrie)" title="Isometrie (Riemannsche Geometrie)">Isometrie</a></i> eine Abbildung, die die <a href="Riemannsche_Metrik" class="mw-redirect" title="Riemannsche Metrik">riemannsche Metrik</a> erhält, und damit nur die Längen von Vektoren und die Längen von Kurven. Eine solche Abbildung braucht nicht die Abstände zwischen zwei Punkten zu erhalten.
</p>

<div class="mw-heading mw-heading2"><h2 id="Definition">Definition</h2></div>
<p>Sind zwei metrische Räume <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 (M_{1},d_{1})}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
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<mo>,</mo>
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<mn>1</mn>
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</msub>
<mo stretchy="false">)</mo>
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<annotation encoding="application/x-tex">{\displaystyle (M_{1},d_{1})}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/94d3c0aca0772489db301d6c287dc52c5545bc75.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:8.415ex; height:2.843ex;" alt="{\displaystyle (M_{1},d_{1})}" loading="lazy"></span>, <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 (M_{2},d_{2})}">
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<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo stretchy="false">(</mo>
<msub>
<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
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<mo>,</mo>
<msub>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
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<mo stretchy="false">)</mo>
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<annotation encoding="application/x-tex">{\displaystyle (M_{2},d_{2})}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/b05a4c68a67ff10c60270286f08ee4917de29200.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:8.415ex; height:2.843ex;" alt="{\displaystyle (M_{2},d_{2})}" loading="lazy"></span> gegeben und ist <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 f\colon M_{1}\rightarrow M_{2}}">
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<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo>:<!-- : --></mo>
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<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
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<mo stretchy="false">→<!-- → --></mo>
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<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
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<annotation encoding="application/x-tex">{\displaystyle f\colon M_{1}\rightarrow M_{2}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1707e883c59406d2377e75a7270aa99c42eded1a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:12.543ex; height:2.509ex;" alt="{\displaystyle f\colon M_{1}\rightarrow M_{2}}" loading="lazy"></span> eine Abbildung mit der Eigenschaft
</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 d_{2}\left(f(x),f(y)\right)=d_{1}(x,y)\ }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>d</mi>
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<mn>2</mn>
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<mrow>
<mo>(</mo>
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<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>x</mi>
<mo stretchy="false">)</mo>
<mo>,</mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>y</mi>
<mo stretchy="false">)</mo>
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<mo>)</mo>
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<mo>=</mo>
<msub>
<mi>d</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
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<mo stretchy="false">(</mo>
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<mo>,</mo>
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<mtext>&nbsp;</mtext>
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<annotation encoding="application/x-tex">{\displaystyle d_{2}\left(f(x),f(y)\right)=d_{1}(x,y)\ }</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/0704a0df60c16931217ca397ed16c041d9a5008c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:25.425ex; height:2.843ex;" alt="{\displaystyle d_{2}\left(f(x),f(y)\right)=d_{1}(x,y)\ }" loading="lazy"></span> für alle <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 x,y\in M_{1}}">
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<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>x</mi>
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<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
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<annotation encoding="application/x-tex">{\displaystyle x,y\in M_{1}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/4149b3f70cd2224c3ba8bdc134103e9a269b9096.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.668ex; height:2.509ex;" alt="{\displaystyle x,y\in M_{1}}" loading="lazy"></span>,</dd></dl>
<p>dann heißt <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 f}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
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<annotation encoding="application/x-tex">{\displaystyle f}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/132e57acb643253e7810ee9702d9581f159a1c61.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}" loading="lazy"></span> <i>Isometrie</i> von <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 M_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
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</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle M_{1}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/577d686fc81d1d1eb3ae54e78aeee8957baf6718.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.308ex; height:2.509ex;" alt="{\displaystyle M_{1}}" loading="lazy"></span> nach <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 M_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
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</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle M_{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/0d5d4dffae5ee0db4cc433e252ee9ed7530e5cf0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.308ex; height:2.509ex;" alt="{\displaystyle M_{2}}" loading="lazy"></span>. Eine solche Abbildung ist stets <a href="Injektivit%C3%A4t" class="mw-redirect" title="Injektivität">injektiv</a>. Ist <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 f}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
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<annotation encoding="application/x-tex">{\displaystyle f}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/132e57acb643253e7810ee9702d9581f159a1c61.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}" loading="lazy"></span> sogar <a href="Bijektivit%C3%A4t" class="mw-redirect" title="Bijektivität">bijektiv</a>, dann heißt <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 f}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
</mstyle>
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<annotation encoding="application/x-tex">{\displaystyle f}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/132e57acb643253e7810ee9702d9581f159a1c61.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}" loading="lazy"></span> <a href="Isometrischer_Isomorphismus" class="mw-redirect" title="Isometrischer Isomorphismus">isometrischer Isomorphismus</a>, und die Räume <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 M_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
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</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle M_{1}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/577d686fc81d1d1eb3ae54e78aeee8957baf6718.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.308ex; height:2.509ex;" alt="{\displaystyle M_{1}}" loading="lazy"></span> und <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 M_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
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</msub>
</mstyle>
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<annotation encoding="application/x-tex">{\displaystyle M_{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/0d5d4dffae5ee0db4cc433e252ee9ed7530e5cf0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.308ex; height:2.509ex;" alt="{\displaystyle M_{2}}" loading="lazy"></span> heißen isometrisch isomorph; andernfalls nennt man <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 f}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
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<annotation encoding="application/x-tex">{\displaystyle f}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/132e57acb643253e7810ee9702d9581f159a1c61.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}" loading="lazy"></span> eine isometrische <a href="Einbettung_(Mathematik)" title="Einbettung (Mathematik)">Einbettung</a> von <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 M_{1}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>M</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
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</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle M_{1}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/577d686fc81d1d1eb3ae54e78aeee8957baf6718.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.308ex; height:2.509ex;" alt="{\displaystyle M_{1}}" loading="lazy"></span> in <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 M_{2}}">
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<mrow class="MJX-TeXAtom-ORD">
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<annotation encoding="application/x-tex">{\displaystyle M_{2}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/0d5d4dffae5ee0db4cc433e252ee9ed7530e5cf0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.308ex; height:2.509ex;" alt="{\displaystyle M_{2}}" loading="lazy"></span>.
</p>
<div class="mw-heading mw-heading2"><h2 id="Spezialfälle"><span id="Spezialf.C3.A4lle"></span>Spezialfälle</h2></div>
<div class="mw-heading mw-heading3"><h3 id="Normierte_Vektorräume"><span id="Normierte_Vektorr.C3.A4ume"></span>Normierte Vektorräume</h3></div>
<p>In <a href="Normierter_Raum" title="Normierter Raum">normierten Vektorräumen</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 V}">
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<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span> ist der Abstand zwischen zwei Vektoren <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 u,v\in V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>u</mi>
<mo>,</mo>
<mi>v</mi>
<mo>∈<!-- ∈ --></mo>
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle u,v\in V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/7acb96be1087c3c2f30d303aa4cac24f62f45daf.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:8.119ex; height:2.509ex;" alt="{\displaystyle u,v\in V}" loading="lazy"></span> durch die <a href="Norm_(Mathematik)" title="Norm (Mathematik)">Norm</a> des Differenzvektors definiert:
</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 d(u,v)=\|v-u\|}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>d</mi>
<mo stretchy="false">(</mo>
<mi>u</mi>
<mo>,</mo>
<mi>v</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mi>v</mi>
<mo>−<!-- − --></mo>
<mi>u</mi>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle d(u,v)=\|v-u\|}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/346ba33b620b6c916ea484d57022ae53942c18f5.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:17.237ex; height:2.843ex;" alt="{\displaystyle d(u,v)=\|v-u\|}" loading="lazy"></span>.</dd></dl>
<p>Sind <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 V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span> und <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 W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/54a9c4c547f4d6111f81946cad242b18298d70b7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\displaystyle W}" loading="lazy"></span> zwei normierte Vektorräume mit Norm <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 \|\cdot \|_{V}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mo>⋅<!-- ⋅ --></mo>
<msub>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>V</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \|\cdot \|_{V}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/4a94815a55b53ec1446f1f7df2afc4fdd55038ba.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.5ex; height:2.843ex;" alt="{\displaystyle \|\cdot \|_{V}}" loading="lazy"></span> bzw. <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 \|\cdot \|_{W}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mo>⋅<!-- ⋅ --></mo>
<msub>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>W</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \|\cdot \|_{W}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/d1ac0304adb0b7e9ba2c8aae7233b46a55947294.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.958ex; height:2.843ex;" alt="{\displaystyle \|\cdot \|_{W}}" loading="lazy"></span> und ist <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 f\colon V\to W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo>:<!-- : --></mo>
<mi>V</mi>
<mo stretchy="false">→<!-- → --></mo>
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle f\colon V\to W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/fa58648b9aa9476995b2b41de27a9a591e631f56.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.149ex; height:2.509ex;" alt="{\displaystyle f\colon V\to W}" loading="lazy"></span> eine <a href="Lineare_Abbildung" title="Lineare Abbildung">lineare Abbildung</a>, so ist diese Abbildung genau dann eine <i>lineare Isometrie</i>, wenn sie die Norm erhält, wenn also für alle <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 v\in V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>v</mi>
<mo>∈<!-- ∈ --></mo>
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle v\in V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/99886ebbde63daa0224fb9bf56fa11b3c8a6f4fb.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:5.756ex; height:2.176ex;" alt="{\displaystyle v\in V}" loading="lazy"></span>
</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 \|f(v)\|_{W}=\|v\|_{V}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>v</mi>
<mo stretchy="false">)</mo>
<msub>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>W</mi>
</mrow>
</msub>
<mo>=</mo>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mi>v</mi>
<msub>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>V</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \|f(v)\|_{W}=\|v\|_{V}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/291fb49840ec45e10644fa8fcaddd6351b6e223c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:16.542ex; height:2.843ex;" alt="{\displaystyle \|f(v)\|_{W}=\|v\|_{V}}" loading="lazy"></span></dd></dl>
<p>gilt.
</p><p>Ohne die Voraussetzung der Linearität gilt für reelle normierte Vektorräume:
</p>
<ul><li>Wenn die Norm <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 \|\cdot \|_{W}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mo>⋅<!-- ⋅ --></mo>
<msub>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>W</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \|\cdot \|_{W}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/d1ac0304adb0b7e9ba2c8aae7233b46a55947294.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.958ex; height:2.843ex;" alt="{\displaystyle \|\cdot \|_{W}}" loading="lazy"></span> des Zielraums strikt konvex ist, ist jede Isometrie <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 V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span> nach <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 W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/54a9c4c547f4d6111f81946cad242b18298d70b7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\displaystyle W}" loading="lazy"></span> eine <a href="Affine_Abbildung" title="Affine Abbildung">affine Abbildung</a>.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></li>
<li>Jede <a href="Surjektive_Funktion" title="Surjektive Funktion">surjektive</a> Isometrie ist eine affine Abbildung (<a href="Satz_von_Mazur-Ulam" title="Satz von Mazur-Ulam">Satz von Mazur-Ulam</a>).<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></li></ul>
<p>In beiden Fällen gilt:
Bildet die Abbildung den <a href="Nullvektor" title="Nullvektor">Nullvektor</a> von <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 V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span> auf den Nullvektor von <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 W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/54a9c4c547f4d6111f81946cad242b18298d70b7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\displaystyle W}" loading="lazy"></span> ab, so ist sie linear.
</p>
<div class="mw-heading mw-heading3"><h3 id="Vektorräume_mit_Skalarprodukt"><span id="Vektorr.C3.A4ume_mit_Skalarprodukt"></span>Vektorräume mit Skalarprodukt</h3></div>
<p>Ist <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 V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span> ein Vektorraum mit <a href="Skalarprodukt" title="Skalarprodukt">Skalarprodukt</a>, so ist die <a href="Skalarproduktnorm" title="Skalarproduktnorm">induzierte Norm</a> (Länge) eines Vektors definiert als die Quadratwurzel aus dem Skalarprodukt des Vektors mit sich selbst. Für den Abstand zweier Vektoren <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 u}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>u</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle u}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c3e6bb763d22c20916ed4f0bb6bd49d7470cffd8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.33ex; height:1.676ex;" alt="{\displaystyle u}" loading="lazy"></span> und <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 v}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>v</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle v}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/e07b00e7fc0847fbd16391c778d65bc25c452597.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.128ex; height:1.676ex;" alt="{\displaystyle v}" loading="lazy"></span> ergibt sich dann:
</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 d(u,v)=\|v-u\|={\sqrt {\langle u-v,u-v\rangle }}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>d</mi>
<mo stretchy="false">(</mo>
<mi>u</mi>
<mo>,</mo>
<mi>v</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mi>v</mi>
<mo>−<!-- − --></mo>
<mi>u</mi>
<mo fence="false" stretchy="false">‖<!-- ‖ --></mo>
<mo>=</mo>
<mrow class="MJX-TeXAtom-ORD">
<msqrt>
<mo fence="false" stretchy="false">⟨<!-- ⟨ --></mo>
<mi>u</mi>
<mo>−<!-- − --></mo>
<mi>v</mi>
<mo>,</mo>
<mi>u</mi>
<mo>−<!-- − --></mo>
<mi>v</mi>
<mo fence="false" stretchy="false">⟩<!-- ⟩ --></mo>
</msqrt>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle d(u,v)=\|v-u\|={\sqrt {\langle u-v,u-v\rangle }}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/aeec2a3eaf375826614bc8260044893fb20cedac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:36.098ex; height:4.843ex;" alt="{\displaystyle d(u,v)=\|v-u\|={\sqrt {\langle u-v,u-v\rangle }}}" loading="lazy"></span>,</dd></dl>
<p>wobei das Skalarprodukt hier durch spitze Klammern bezeichnet wird.
</p><p>Sind <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 V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span> und <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 W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/54a9c4c547f4d6111f81946cad242b18298d70b7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\displaystyle W}" loading="lazy"></span> Vektorräume mit Skalarprodukt <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 \langle \cdot ,\cdot \rangle _{V}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">⟨<!-- ⟨ --></mo>
<mo>⋅<!-- ⋅ --></mo>
<mo>,</mo>
<mo>⋅<!-- ⋅ --></mo>
<msub>
<mo fence="false" stretchy="false">⟩<!-- ⟩ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>V</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \langle \cdot ,\cdot \rangle _{V}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/3c62dcc2d580ec7c82101d231955db6ad6de9353.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.633ex; height:2.843ex;" alt="{\displaystyle \langle \cdot ,\cdot \rangle _{V}}" loading="lazy"></span> bzw. <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 \langle \cdot ,\cdot \rangle _{W}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">⟨<!-- ⟨ --></mo>
<mo>⋅<!-- ⋅ --></mo>
<mo>,</mo>
<mo>⋅<!-- ⋅ --></mo>
<msub>
<mo fence="false" stretchy="false">⟩<!-- ⟩ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>W</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \langle \cdot ,\cdot \rangle _{W}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/6a10389436226626f3b480b381202daf4ccb7881.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:6.091ex; height:2.843ex;" alt="{\displaystyle \langle \cdot ,\cdot \rangle _{W}}" loading="lazy"></span> und ist <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 f\colon V\to W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo>:<!-- : --></mo>
<mi>V</mi>
<mo stretchy="false">→<!-- → --></mo>
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle f\colon V\to W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/fa58648b9aa9476995b2b41de27a9a591e631f56.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.149ex; height:2.509ex;" alt="{\displaystyle f\colon V\to W}" loading="lazy"></span> eine lineare Abbildung,
so ist diese Abbildung genau dann eine lineare Isometrie, wenn sie das Skalarprodukt erhält, das heißt
</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 \langle f(u),f(v)\rangle _{W}=\langle u,v\rangle _{V}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">⟨<!-- ⟨ --></mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>u</mi>
<mo stretchy="false">)</mo>
<mo>,</mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>v</mi>
<mo stretchy="false">)</mo>
<msub>
<mo fence="false" stretchy="false">⟩<!-- ⟩ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>W</mi>
</mrow>
</msub>
<mo>=</mo>
<mo fence="false" stretchy="false">⟨<!-- ⟨ --></mo>
<mi>u</mi>
<mo>,</mo>
<mi>v</mi>
<msub>
<mo fence="false" stretchy="false">⟩<!-- ⟩ --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi>V</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \langle f(u),f(v)\rangle _{W}=\langle u,v\rangle _{V}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/512cd3458f79cafe1becdb79ec81610ce20ae504.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:23.326ex; height:2.843ex;" alt="{\displaystyle \langle f(u),f(v)\rangle _{W}=\langle u,v\rangle _{V}}" loading="lazy"></span> für alle <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 u,v\in V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>u</mi>
<mo>,</mo>
<mi>v</mi>
<mo>∈<!-- ∈ --></mo>
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle u,v\in V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/7acb96be1087c3c2f30d303aa4cac24f62f45daf.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:8.119ex; height:2.509ex;" alt="{\displaystyle u,v\in V}" loading="lazy"></span>.</dd></dl>
<p>Solche Abbildungen werden auch <a href="Orthogonale_Abbildung" title="Orthogonale Abbildung">orthogonale Abbildungen</a> (im Fall reeller Skalarprodukträume) oder <a href="Unit%C3%A4re_Abbildung" title="Unitäre Abbildung">unitäre Abbildungen</a> (im Fall komplexer Skalarprodukträume) genannt. Bei reellen Skalarprodukträumen muss dabei nicht vorausgesetzt werden, dass die Abbildung linear ist, denn jede Isometrie, die den Nullvektor auf den Nullvektor abbildet, ist in diesem Fall linear.
</p><p>Ist <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_{1},\ldots ,a_{n}\}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">{</mo>
<msub>
<mi>a</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<mo>…<!-- … --></mo>
<mo>,</mo>
<msub>
<mi>a</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>n</mi>
</mrow>
</msub>
<mo fence="false" stretchy="false">}</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \{a_{1},\ldots ,a_{n}\}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/f985892ccc9f753dc96b7da26722b0cb302bdcc9.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:12.235ex; height:2.843ex;" alt="{\displaystyle \{a_{1},\ldots ,a_{n}\}}" loading="lazy"></span> eine <a href="Orthonormalbasis" title="Orthonormalbasis">Orthonormalbasis</a> von <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 V}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>V</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/af0f6064540e84211d0ffe4dac72098adfa52845.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.787ex; height:2.176ex;" alt="{\displaystyle V}" loading="lazy"></span>, so ist eine lineare Abbildung <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 f\colon V\to W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo>:<!-- : --></mo>
<mi>V</mi>
<mo stretchy="false">→<!-- → --></mo>
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle f\colon V\to W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/fa58648b9aa9476995b2b41de27a9a591e631f56.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.149ex; height:2.509ex;" alt="{\displaystyle f\colon V\to W}" loading="lazy"></span> genau dann eine Isometrie, wenn
<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 \{f(a_{1}),\ldots ,f(a_{n})\}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mo fence="false" stretchy="false">{</mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<msub>
<mi>a</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo>,</mo>
<mo>…<!-- … --></mo>
<mo>,</mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<msub>
<mi>a</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>n</mi>
</mrow>
</msub>
<mo stretchy="false">)</mo>
<mo fence="false" stretchy="false">}</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle \{f(a_{1}),\ldots ,f(a_{n})\}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/ce7fb5a7c951d6708fe58b4752bae9429f298c14.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:18.411ex; height:2.843ex;" alt="{\displaystyle \{f(a_{1}),\ldots ,f(a_{n})\}}" loading="lazy"></span> ein <a href="Orthonormalsystem" class="mw-redirect" title="Orthonormalsystem">Orthonormalsystem</a> in <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 W}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>W</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle W}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/54a9c4c547f4d6111f81946cad242b18298d70b7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.435ex; height:2.176ex;" alt="{\displaystyle W}" loading="lazy"></span> ist.
</p><p>Die Menge aller linearen Isometrien eines euklidischen Vektorraums in sich bildet eine <a href="Gruppe_(Mathematik)" title="Gruppe (Mathematik)">Gruppe</a>, die <a href="Orthogonale_Gruppe" title="Orthogonale Gruppe">orthogonale Gruppe</a> des Raums. Entsprechend bildet die Menge aller linearen Isometrien eines unitären Vektorraums in sich die <a href="Unit%C3%A4re_Gruppe" title="Unitäre Gruppe">unitäre Gruppe</a> des Raums.
</p>
<div class="mw-heading mw-heading3"><h3 id="Euklidischer_Punktraum">Euklidischer Punktraum</h3></div>
<div class="hauptartikel" role="navigation"><span class="hauptartikel-pfeil" title="siehe" aria-hidden="true" role="presentation">→&nbsp;</span><i><span class="hauptartikel-text">Hauptartikel</span>: <a href="Bewegung_(Mathematik)" title="Bewegung (Mathematik)">Bewegung (Mathematik)</a></i></div>
<p>Jede Isometrie <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 f\colon E\to F}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo>:<!-- : --></mo>
<mi>E</mi>
<mo stretchy="false">→<!-- → --></mo>
<mi>F</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle f\colon E\to F}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/65e588635af63181c20287f8ea6f18389b5eaec2.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.443ex; height:2.509ex;" alt="{\displaystyle f\colon E\to F}" loading="lazy"></span> zwischen zwei <a href="Euklidischer_Punktraum" class="mw-redirect" title="Euklidischer Punktraum">euklidischen Punkträumen</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 E}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>E</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle E}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/4232c9de2ee3eec0a9c0a19b15ab92daa6223f9b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.776ex; height:2.176ex;" alt="{\displaystyle E}" loading="lazy"></span> und <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 F}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>F</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle F}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/545fd099af8541605f7ee55f08225526be88ce57.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.741ex; height:2.176ex;" alt="{\displaystyle F}" loading="lazy"></span> ist eine <a href="Affine_Abbildung" title="Affine Abbildung">affine Abbildung</a>. Sie lässt sich in der Form
</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 f(Q)=f(P)+{\vec {f}}({\overrightarrow {PQ}})}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>Q</mi>
<mo stretchy="false">)</mo>
<mo>=</mo>
<mi>f</mi>
<mo stretchy="false">(</mo>
<mi>P</mi>
<mo stretchy="false">)</mo>
<mo>+</mo>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>f</mi>
<mo stretchy="false">→<!-- → --></mo>
</mover>
</mrow>
</mrow>
<mo stretchy="false">(</mo>
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mrow>
<mi>P</mi>
<mi>Q</mi>
</mrow>
<mo>→<!-- → --></mo>
</mover>
</mrow>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle f(Q)=f(P)+{\vec {f}}({\overrightarrow {PQ}})}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/5cddb2a3be82505dd28f28f65addc916dca2536b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; margin-top: -0.4ex; width:22.886ex; height:4.343ex;" alt="{\displaystyle f(Q)=f(P)+{\vec {f}}({\overrightarrow {PQ}})}" loading="lazy"></span> für alle <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 P,Q\in E}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>P</mi>
<mo>,</mo>
<mi>Q</mi>
<mo>∈<!-- ∈ --></mo>
<mi>E</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P,Q\in E}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/2c4926c8211657ca4cb031f138c20e5adc8a5f94.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.234ex; height:2.509ex;" alt="{\displaystyle P,Q\in E}" loading="lazy"></span></dd></dl>
<p>darstellen, wobei <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 {f}}\colon V_{E}\to V_{F}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mi>f</mi>
<mo stretchy="false">→<!-- → --></mo>
</mover>
</mrow>
</mrow>
<mo>:<!-- : --></mo>
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>E</mi>
</mrow>
</msub>
<mo stretchy="false">→<!-- → --></mo>
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>F</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\vec {f}}\colon V_{E}\to V_{F}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/cb6e0da398c643d1d0467aef38a13496396f0182.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:11.974ex; height:3.343ex;" alt="{\displaystyle {\vec {f}}\colon V_{E}\to V_{F}}" loading="lazy"></span> eine lineare Isometrie zwischen den zugehörigen euklidischen Vektorräumen <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 V_{E}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>E</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V_{E}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/b327692ccc05af0bf8f8fdf45b159d0e6ed849ef.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.843ex; height:2.509ex;" alt="{\displaystyle V_{E}}" loading="lazy"></span> und <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 V_{F}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>V</mi>
<mrow class="MJX-TeXAtom-ORD">
<mi>F</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle V_{F}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/fa88fb1d8dc67b97da3e5eaea9bc6c2d385abbaa.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.818ex; height:2.509ex;" alt="{\displaystyle V_{F}}" loading="lazy"></span> ist.
</p><p>Umgekehrt ist jede Abbildung, die sich so darstellen lässt, eine Isometrie.
Isometrien eines euklidischen Punktraums in sich heißen auch <i>Bewegungen</i>.
</p>
<div class="mw-heading mw-heading3"><h3 id="Beispiel_einer_nicht_surjektiven_Isometrie">Beispiel einer nicht surjektiven Isometrie</h3></div>
<p>Bezüglich der <a href="Diskrete_Metrik" class="mw-redirect" title="Diskrete Metrik">diskreten Metrik</a> ist jede injektive Abbildung <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 f\colon \mathbb {N} \rightarrow \mathbb {N} }">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo>:<!-- : --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="double-struck">N</mi>
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<mo stretchy="false">→<!-- → --></mo>
<mrow class="MJX-TeXAtom-ORD">
<mi mathvariant="double-struck">N</mi>
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<annotation encoding="application/x-tex">{\displaystyle f\colon \mathbb {N} \rightarrow \mathbb {N} }</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1979eb274d7f0643cb28b0038fbd78d133288a78.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:9.283ex; height:2.509ex;" alt="{\displaystyle f\colon \mathbb {N} \rightarrow \mathbb {N} }" loading="lazy"></span> eine Isometrie. Somit ist die durch <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 f(n)=2n}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>f</mi>
<mo stretchy="false">(</mo>
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<mi>n</mi>
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<annotation encoding="application/x-tex">{\displaystyle f(n)=2n}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/2d7988767ca9a25a6a97a528227815e76d71e676.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:10.138ex; height:2.843ex;" alt="{\displaystyle f(n)=2n}" loading="lazy"></span> definierte Abbildung eine nicht surjektive Isometrie.
</p><p>Ein anderes Beispiel einer nicht surjektiven Isometrie ist die Inklusion einer echten Teilmenge <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 \iota \colon Y\subset X}">
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<annotation encoding="application/x-tex">{\displaystyle \iota \colon Y\subset X}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c9d92ed3f3be2584eb3d082cb42fe81828952cbc.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:8.709ex; height:2.176ex;" alt="{\displaystyle \iota \colon Y\subset X}" loading="lazy"></span> eines beliebigen metrischen Raumes <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 (X,d)}">
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<mrow class="MJX-TeXAtom-ORD">
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<annotation encoding="application/x-tex">{\displaystyle (X,d)}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/cb4d7a16bca9e216c0221b43a1c3377aa5e358b8.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:6.039ex; height:2.843ex;" alt="{\displaystyle (X,d)}" loading="lazy"></span>, wobei die Metrik auf <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 Y}">
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<mi>Y</mi>
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<annotation encoding="application/x-tex">{\displaystyle Y}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/961d67d6b454b4df2301ac571808a3538b3a6d3f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.171ex; width:1.773ex; height:2.009ex;" alt="{\displaystyle Y}" loading="lazy"></span> durch <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\mid _{Y\times Y}}">
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<annotation encoding="application/x-tex">{\displaystyle d\mid _{Y\times Y}}</annotation>
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</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/20a33460daa5670a88554924c43132431d034dac.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.881ex; height:2.843ex;" alt="{\displaystyle d\mid _{Y\times Y}}" loading="lazy"></span> gegeben sei.
</p>
<div class="mw-heading mw-heading2"><h2 id="Weitere_Eigenschaften">Weitere Eigenschaften</h2></div>
<ul><li>Aus der Definition folgt unmittelbar, dass jede Isometrie stetig ist.</li>
<li>Jede Isometrie ist sogar <a href="Lipschitz-Stetigkeit" class="mw-redirect" title="Lipschitz-Stetigkeit">Lipschitz-stetig</a>, also insbesondere <a href="Gleichm%C3%A4%C3%9Fige_Stetigkeit" title="Gleichmäßige Stetigkeit">gleichmäßig stetig</a>. Isometrien sind damit stetig fortsetzbar auf den Abschluss, wenn der Bildraum <a href="Vollst%C3%A4ndiger_Raum" title="Vollständiger Raum">vollständig</a> ist.</li>
<li>Jeder metrische Raum ist isometrisch isomorph zu einer abgeschlossenen Teilmenge eines normierten Vektorraums, und jeder vollständige metrische Raum ist isometrisch isomorph zu einer abgeschlossenen Teilmenge eines <a href="Banachraum" title="Banachraum">Banachraums</a>.</li>
<li>Jede Isometrie zwischen zwei euklidischen Räumen erhält auch <a href="Winkel" title="Winkel">Winkel</a>, <a href="Fl%C3%A4cheninhalt" title="Flächeninhalt">Flächeninhalt</a> und <a href="Volumen" title="Volumen">Volumen</a>.</li>
<li>Können in euklidischen Räumen zwei Figuren durch eine Isometrie aufeinander abgebildet werden, so heißen die Figuren isometrisch. Zwei Figuren, die durch eine Bewegung aufeinander abgebildet werden können, nennt man <a href="Kongruenz_(Geometrie)" title="Kongruenz (Geometrie)">kongruent</a>.</li>
<li>Allgemein erhält jede Isometrie zwischen metrischen Räumen die <a href="Hausdorff-Ma%C3%9F" title="Hausdorff-Maß">Hausdorff-Maße</a>.</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Siehe_auch">Siehe auch</h2></div>
<ul><li><a href="Quasi-Isometrie" title="Quasi-Isometrie">Quasi-Isometrie</a></li>
<li><a href="Ingenieurperspektive" title="Ingenieurperspektive">Ingenieurperspektive</a> oder Dimetrie</li>
<li><a href="Kavalierperspektive" title="Kavalierperspektive">Kavalierperspektive</a></li>
<li><a href="Milit%C3%A4rperspektive" title="Militärperspektive">Militärperspektive</a></li>
<li><a href="Perspektive" title="Perspektive">Perspektive</a></li>
<li><a href="Axonometrie" title="Axonometrie">Axonometrie</a> (<a href="Isometrie_(Perspektiveart)" title="Isometrie (Perspektiveart)">isometrische Axonometrie</a>)</li>
<li><a href="Isometrische_Perspektive_in_Computerspielen" title="Isometrische Perspektive in Computerspielen">Isometrische Perspektive in Computerspielen</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="Literatur">Literatur</h2></div>
<ul><li><a href="Siegfried_Bosch" title="Siegfried Bosch">Siegfried Bosch</a>: <i>Lineare Algebra</i>. 2. überarbeitete Auflage. Springer, Berlin u. a. 2003, ISBN 3-540-00121-2, (<i>Springer-Lehrbuch</i>).</li>
<li>Fritz Reinhardt, Heinrich Soeder: <cite style="font-style:italic">dtv-Atlas zur Mathematik. Tafeln und Texte</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>1</span>. 9. Auflage. Deutscher Taschenbuch Verlag, München 1991, ISBN 3-423-03007-0.<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rfr_id=info:sid/de.wikipedia.org:Isometrie&amp;rft.au=Fritz+Reinhardt%2C+Heinrich+Soeder&amp;rft.btitle=dtv-Atlas+zur+Mathematik.+Tafeln+und+Texte&amp;rft.date=1991&amp;rft.genre=book&amp;rft.isbn=3423030070&amp;rft.place=M%C3%BCnchen&amp;rft.pub=Deutscher+Taschenbuch+Verlag&amp;rft.volume=Band+1.+9.+Auflage" style="display:none">&nbsp;</span></li></ul>
<div class="mw-heading mw-heading2"><h2 id="Einzelnachweise">Einzelnachweise</h2></div>
<ol class="references">
<li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text">Wissenschaftlicher Rat der Dudenredaktion (Hrsg.): <cite style="font-style:italic">Duden. Das große Fremdwörterbuch.</cite> 4., aktualisierte Auflage. Dudenverlag, Mannheim / Leipzig / Wien / Zürich 2007, ISBN 978-3-411-04164-0, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>659</span>.<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rfr_id=info:sid/de.wikipedia.org:Isometrie&amp;rft.btitle=Duden.+Das+gro%C3%9Fe+Fremdw%C3%B6rterbuch.&amp;rft.date=2007&amp;rft.edition=4.%2C+aktualisierte&amp;rft.genre=book&amp;rft.isbn=9783411041640&amp;rft.pages=659&amp;rft.place=Mannheim+%2F+Leipzig+%2F+Wien+%2F+Z%C3%BCrich&amp;rft.pub=Dudenverlag" style="display:none">&nbsp;</span></span>
</li>
<li id="cite_note-2"><span class="mw-cite-backlink"><a href="#cite_ref-2">↑</a></span> <span class="reference-text"><span class="cite">Jussi Väisälä: <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140221153229/http://www.helsinki.fi/~jvaisala/mazurulam.pdf"><i>A proof of the Mazur-Ulam theorem.</i></a> (PDF) <span style="white-space:nowrap;">S. 2</span>, archiviert vom <style data-mw-deduplicate="TemplateStyles:r250917974">
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</style><span class="dewiki-iconexternal"><a class="external text" href="https://redirecter.toolforge.org/?url=http%3A%2F%2Fwww.helsinki.fi%2F%7Ejvaisala%2Fmazurulam.pdf">Original</a></span> am <span style="white-space:nowrap;">21.&nbsp;Februar 2014</span><span>;</span><span class="Abrufdatum"> abgerufen am 9.&nbsp;November 2024</span>.</span><span style="display: none;" class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&amp;rfr_id=info%3Asid%2Fde.wikipedia.org%3AIsometrie&amp;rft.title=A+proof+of+the+Mazur-Ulam+theorem&amp;rft.description=A+proof+of+the+Mazur-Ulam+theorem&amp;rft.identifier=https%3A%2F%2Fweb.archive.org%2Fweb%2F20140221153229%2Fhttp%3A%2F%2Fwww.helsinki.fi%2F%7Ejvaisala%2Fmazurulam.pdf&amp;rft.creator=Jussi+V%C3%A4is%C3%A4l%C3%A4&amp;rft.source=http://www.helsinki.fi/~jvaisala/mazurulam.pdf">&nbsp;</span></span>
</li>
<li id="cite_note-3"><span class="mw-cite-backlink"><a href="#cite_ref-3">↑</a></span> <span class="reference-text">Stanisław Mazur, Stanisław Ulam: <cite style="font-style:italic">Sur les transformationes isométriques d’espaces vectoriels normés</cite>. In: <cite style="font-style:italic">C. R. Acad. Sci. Paris</cite>. <span style="white-space:nowrap">Band<span style="display:inline-block;width:.2em">&nbsp;</span>194</span>, 1932, <span style="white-space:nowrap">S.<span style="display:inline-block;width:.2em">&nbsp;</span>946–948</span>.<span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rfr_id=info:sid/de.wikipedia.org:Isometrie&amp;rft.atitle=Sur+les+transformationes+isom%C3%A9triques+d%E2%80%99espaces+vectoriels+norm%C3%A9s&amp;rft.au=Stanis%C5%82aw+Mazur%2C+Stanis%C5%82aw+Ulam&amp;rft.btitle=C.+R.+Acad.+Sci.+Paris&amp;rft.date=1932&amp;rft.genre=book&amp;rft.pages=946-948&amp;rft.volume=194" style="display:none">&nbsp;</span></span>
</li>
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