Polygon with ten sides.
Properties
A decagon has ten interior angles and 35 diagonals.
If the decagon is a regular decagon, then each of its interior angles measures 144°.
The apothem a of a regular decagon with a side length of c units is \(a = dfrac{c}{2 tan (frac{π}{10})}\)
Formula
The formula to calculate the area A of a regular decagon of side length c is:
\( A=frac{5}{2}a^{2}sqrt{5+2sqrt{5}} \)
Examples
General decagon
Regular decagon
