Polygon with nine sides.
A nonagon has 9 sides and 9 interior angles. If it is a regular nonagon, each of its interior angles measures 140°.
Formula
The formula to calculate the area A of a regular nonagon with a side length of c is :
\(\frac{9{c}^{2}}{4}\textrm{cot(π/9)}\)
Examples
This is a regular nonagon :
This is an irregular nonagon :
