# Nonagon

## Nonagon

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 :