Creation of this applet was inspired by a [url=https://twitter.com/gogeometry/status/849823013767983104]tweet[/url] from [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url]. [br][br]What is the sum of the measures of the [b][color=#cc0000]red angle[/color][/b] and [color=#0000ff][b]blue angle[/b][/color]? [br][color=#9900ff][b]How can you formally prove this true? [/b][/color]