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Difference between revisions of "Euler theorem"

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For every polyhedron the number <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366101.png" /> of its vertices plus the number <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366102.png" /> of its faces minus the number <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366103.png" /> of its edges is equal to 2:
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For every polyhedron the number $V$ of its vertices plus the number $F$ of its faces minus the number $E$ of its edges is equal to 2:
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366104.png" /></td> <td valign="top" style="width:5%;text-align:right;">(*)</td></tr></table>
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$$V+F-E=2.\label{*}\tag{*}$$
  
Euler's theorem hold for polyhedrons of genus <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366105.png" />; for polyhedrons of genus <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366106.png" /> the relation
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Euler's theorem hold for polyhedrons of genus $0$; for polyhedrons of genus $p$ the relation
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036610/e0366107.png" /></td> </tr></table>
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$$V+F-E=2-2p$$
  
holds. This theorem was proved by L. Euler (1758); the relation (*) was known to R. Descartes (1620).
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holds. This theorem was proved by L. Euler (1758); the relation \eqref{*} was known to R. Descartes (1620).
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[[Category:Geometry]]

Latest revision as of 17:34, 14 February 2020

For every polyhedron the number $V$ of its vertices plus the number $F$ of its faces minus the number $E$ of its edges is equal to 2:

$$V+F-E=2.\label{*}\tag{*}$$

Euler's theorem hold for polyhedrons of genus $0$; for polyhedrons of genus $p$ the relation

$$V+F-E=2-2p$$

holds. This theorem was proved by L. Euler (1758); the relation \eqref{*} was known to R. Descartes (1620).

How to Cite This Entry:
Euler theorem. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Euler_theorem&oldid=18548
This article was adapted from an original article by A.B. Ivanov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article