Creation of this applet came from two sources: [br][br]1) This [url=https://twitter.com/gogeometry/status/850846787539804162]tweet[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry)[br][br]2) This [url=https://twitter.com/CutTheKnotMath/status/957241488039206912]tweet[/url] from [url=https://twitter.com/CutTheKnotMath]Alexander Bogomolny[/url] (Cut-the-Knot Math)[br][br][b][color=#0000ff]How can we formally prove the phenomena dynamically illustrated here? [/color][/b][br][br]