Creation of this resource was inspired by [url=http://www.gogeometry.com/problem/p232_parallelogram_perpendicular_lines.htm]this problem[/url] posed by [url=https://twitter.com/gogeometry]Antonio Gutierrez (GoGeometry)[/url]. [br][br]You can move any of the [b]LARGE POINTS[/b] anywhere you'd like [b]AT ANY TIME[/b].[br][b][color=#ff00ff]The bottom left slider controls the size of the colored angle. [/color][/b][br][br][b]How can we formally prove the phenomenon dynamically illustrated here? [/b][br][br]Is it possible to make the longest perpendicular segment different from what is originally shown? [br]Try to move the points and/or bottom left slider to make this happen.[br]How would you describe what you see now?