

Dynamic Geometry:
Butterfly Theorem Proof: Circle, Chord, Midpoint,
Inscribed Angle, SAS Similarity, Cyclic Quadrilateral,
ASA Congruence. HTML5 Animation for Mobile Devices.

Given two circles of centers A and B, draw the tangents
AC, AD, BE, and BF from the center of each circle to the
other. Then the chords MN and PQ are of equal length.
Static Geometry: Butterfly
Theorem Proof.






