[color=#000000]Creation of this applet was inspired by a [/color][url=https://plus.google.com/photos/photo/117684142435389193789/6323558467726880594?icm=false&sqid=100568607954673744130&ssid=08dae2ec-bc7c-4cd1-a885-aee503ea0e7a]Google Plus Photo[/url][color=#000000] posted by [/color][url=https://www.geogebra.org/jeandavid54]Jean David[/url][color=#000000]. [br][br]How can you formally prove what this applet informally illustrates? [br][/color][b][color=#000000]Note: Feel free to move the BIG WHITE POINT anywhere you'd like on the [/color][color=#1e84cc]BLUE ARC[/color][color=#000000]. [/color][/b]