Decagon

Math

A decagon is a polygon whose internal angle is 1440&deg;. A regular decagon is a decagon that looks like what is in the right (with a side length of 260px).

Measurements
The perimeter of a regular decagon is 10t, where t is the side length of the decagon.

The area of a regular decagon is \(\frac{10t^2}{4\tan{18^\circ}}\approx7.6942t^2\), where t is the side length of the decagon.