GoGeometry Action 35!

Creation of this applet was inspired by a [url=https://twitter.com/gogeometry/status/858339142400389121]tweet[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url]. [br][br][b][color=#0000ff]How can you formally prove the 3 phenomena dynamically illustrated here? [/color][/b]
Quick (Silent) Demo

Information: GoGeometry Action 35!