An Applet for side bisectors of a triangle

This is an applet to look at a theorem in Geometry.
The theorem says that if we take the three perpendicular bisectors of the sides of a triangle, they will all meet in one point. 

Start by moving the points, then add the bisectors and convince yourself that the theorem is true.
Once you are convinced, use the circle to try to construct a proof.

Mike May, S.J., July 11, 2011, Created with GeoGebra