Creation of this applet was inspired by a [url=https://twitter.com/gogeometry/status/848519433970737152]tweet[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url]. [br][br][b]Feel free to move the BIG WHITE POINTS anywhere you'd like. [/b][br][color=#1e84cc][b]Feel free to adjust the slider as well. [/b][/color][br][br][color=#0000ff][b]How can you formally prove what this applet informally illustrates? [/b][/color]