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Difference between revisions of "Excess of a triangle"

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''spherical excess, excess''
 
''spherical excess, excess''
  
The difference between the sum of the angles of a spherical triangle and two right angles. The excess <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036810/e0368101.png" /> of a spherical triangle is proportional to its area <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036810/e0368102.png" />: <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036810/e0368103.png" />, where <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/e/e036/e036810/e0368104.png" /> is the radius of the sphere containing the spherical triangle.
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The difference between the sum of the angles of a spherical triangle and two right angles. The excess $\epsilon$ of a spherical triangle is proportional to its area $S$: $S=R^2\epsilon$, where $R$ is the radius of the sphere containing the spherical triangle.
  
  

Latest revision as of 11:56, 5 July 2014

spherical excess, excess

The difference between the sum of the angles of a spherical triangle and two right angles. The excess $\epsilon$ of a spherical triangle is proportional to its area $S$: $S=R^2\epsilon$, where $R$ is the radius of the sphere containing the spherical triangle.


Comments

This notion is sometimes called the defect of the triangle (cf. Triangle, defect of a).

References

[a1] M. Berger, "Geometry" , II , Springer (1987) pp. 278
[a2] H.S.M. Coxeter, "Non-Euclidean geometry" , Univ. Toronto Press (1957)
[a3] M. Greenberg, "Euclidean and non-Euclidean geometry" , Freeman (1980) pp. 105
How to Cite This Entry:
Excess of a triangle. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Excess_of_a_triangle&oldid=32378
This article was adapted from an original article by A.B. Ivanov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article