GoGeometry Action 130!

Creation of this applet was inspired by a [url=http://www.gogeometry.com/school-college/3/p1278-square-3-4-5-right-triangle-tutoring.htm]problem[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br]You can move the [b]2 LARGE WHITE POINTS[/b] anywhere you'd like at any time. [br][br][b][color=#38761d]How can we formally prove the phenomenon dynamically illustrated here? [/color][/b]
Quick (Silent) Demo

Information: GoGeometry Action 130!