Creation of this resource was inspired by a [url=http://www.gogeometry.com/problem/p741-triangle-incenter-circumcircle-midpoint-arc-chord-congruence.htm]problem[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br]You can move the [b]3 VERTICES[/b] of the triangle anywhere you'd like [b]AT ANY TIME[/b].[br][color=#ff00ff]The pink slider controls the size of the interior angle with pink vertex. [br][br][/color][color=#9900ff][b]How can we formally prove what is dynamically illustrated here? [/b][/color]