This video shows how to construct a regular pentagon inside a circle, using only a ruler and a compass. The circle become the circumcircle of the pentagon. This constructed was selected by a computer to have as few steps as possible.
For more videos and math help, see http://www.dr-mikes-math-games-for-kids.com/
Music "Beachfront Celebration" by Kevin MacLeod, http://www.incompetech.com