Creation of this applet was inspired by this [url=https://twitter.com/gogeometry/status/833690663426326528]tweet[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url]. [br][br]BIG points are moveable, yet all dynamics will be illustrated only if point [i]G[/i] (see [url=https://twitter.com/gogeometry/status/833690663426326528]tweet[/url]) lies ABOVE [color=#38761d][b]the smaller semicircle.[/b][/color] [br][br][b][color=#0000ff]How can you formally prove what this applet informally illustrates? [/color][/b]