Octadecagon

A octadecagon

A octadecagon or 18-gon is a shape with 18 sides and 18 corners.

Regular octadecagon

All sides of a regular octadecagon are the same length. Each corner is 160°. All corners added together equal 2880°.

Area

The amount of space a regular octadecagon takes up is

The area of a regular octadecagon of side length a is given by

$A=\frac{18}{4}{a}^2\cot \frac{\pi }{18}\simeq 25,5208a^2$