Octadecagon
Appearance
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Regular_octadecagon.svg/220px-Regular_octadecagon.svg.png)
A octadecagon or 18-gon is a shape with 18 sides and 18 corners.
Regular octadecagon[change | change source]
All sides of a regular octadecagon are the same length. Each corner is 160°. All corners added together equal 2880°.
Area[change | change source]
The amount of space a regular octadecagon takes up is
The area of a regular octadecagon of side length a is given by