Decagon

A decagon is a polygon with ten sides. A decagon has interior angles of measure $144^{\circ}$, and exterior angles of measure $36^{\circ}$. The area of a regular decagon with side length $a$ is $\frac{5}{2} a^{2} \sqrt{5+2\sqrt{5}}$

See Also

This article is a stub. Help us out by expanding it.