Creation of this applet was originally inspired by a [url=https://twitter.com/solvemymaths/status/830868402965270528]tweet[/url] from [url=https://twitter.com/solvemymaths]Solve My Maths[/url]. [br][br]How does this applet informally illustrate that the [color=#b45f06][b]yellow[/b][/color] and [color=#38761d][b]light green[/b][/color] triangles have equal area? [br][color=#0000ff][br][b]How can you formally prove that the areas of these two triangles are indeed equal? [/b][/color]