Constructible polygon
Regular polygon that can be constructed with compass and straightedge / From Wikipedia, the free encyclopedia
In mathematics, a constructible polygon is a regular polygon that can be constructed with compass and straightedge. For example, a regular pentagon is constructible with compass and straightedge while a regular heptagon is not. There are infinitely many constructible polygons, but only 31 with an odd number of sides are known.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/7/76/Pentagon_construct.gif)