A octadecagon or 18-gon is a shape with 18 sides and 18 corners.
All sides of a regular octadecagon are the same length. Each corner is 160°. All corners added together equal 2880°.
The amount of space a regular octadecagon takes up is
The area of a regular octadecagon of side length a is given by
Images for kids
Octadecagon, an exact construction based on the angle trisection 120° by means of the tomahawk, animation 1 min 34 s.
Symmetries of a regular octadecagon. Vertices are colored by their symmetry positions. Blue mirrors are drawn through vertices, and purple mirrors are drawn through edge. Gyration orders are given in the center.