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Icosagon

Icosagon

A 20-sided polygon. The regular icosagon is a constructible polygon, and the regular icosagon of unit side length has inradius r, circumradius R, and area A given by

r=1/2(1+sqrt(5)+sqrt(5+2sqrt(5)))
(1)
R=sqrt(3+sqrt(5)+1/2sqrt(50+22sqrt(5)))
(2)
A=5(1+sqrt(5)+sqrt(5+2sqrt(5))).
(3)

The swastika is an irregular icosagon.

See also

Swastika, Trigonometry Angles--Pi/20

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Cite this as:

Weisstein, Eric W. "Icosagon." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Icosagon.html

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