Creation of this applet was inspired by a [url=http://eylemmath.weebly.com/calculus/same-angles]post[/url] from [url=http://eylemmath.weebly.com/]eyleMMath[/url]. [br][br]How can we formally prove that the [color=#cc0000][b]measures of the two red angles are equal? [/b][/color] [br][br][color=#0000ff][i]Is this possible to prove without using trigonometry? [/i] [/color]