Creation of this applet was inspired by a [url=https://twitter.com/gogeometry/status/835210435116871680]tweet[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url]. [br][br]Make sure the [b][color=#ff00ff]pink points[/color][/b] are aligned so the [b][color=#666666]secant that passes through them is also a secant[/color][/b] [color=#38761d][b]for the smaller circle! [/b][/color] (Otherwise you won't see the intended phenomena.) [br][br][b][color=#0000ff]How can you formally prove what this applet informally illustrates? [/color][/b]