In mathematical geometry, Decagon is a ten sided polygon. It is also known as 10-gon. A regular decagon has all sides of equal length and each internal angle will always be equal to 144°. Use this online regular decagon calculator to find the area of a regular decagon. To find the area of a decagon just input the area of an equilateral triangle.
A decagon with side length 5 cm has area of
= 5/2 (25)√5 + 2√5
= 192.36 cm2