An icosagon is a 20-sided polygon. The regular icosagon is a constructible polygon, and the regular
icosagon of unit side length has inradius 
, circumradius 
, and area 
given by
 |  |  |
(1)
|
 |  |  |
(2)
|
 |  |  |
(3)
|
The swastika is an irregular icosagon.
