GoGeometry Action 19!

Creation of this applet was inspired by a [url=https://twitter.com/gogeometry/status/849761336695377922]tweet[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url]. [br][br][b]Feel free to move any of the BIG POINTS anywhere you'd like at any time. [/b][br][br][color=#0000ff][b]How can you formally prove what this applet informally illustrates? [/b][/color]
Quick (Silent) Demo

Information: GoGeometry Action 19!