# The Butterfly Theorem

The Butterfly Theorem

Let HE be a chord of a circle and CF and DG be two other chords passing through the midpoint P of HE. If CG and DF intersect HE, denote the points of intersection by A and B. When CG and DF intersect HE, P is the midpoint of AB.

Drag any of the magenta points on the circle to modify the diagram.