Creation of this resource was inspired by this [url=http://www.gogeometry.com/problem/p309_nonagon_diagonal_side_sum.htm]problem[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br]You can move the [b]2 LARGE WHITE VERTICES[/b] anywhere you'd like at any time. [br][br][b]How can we formally prove the phenomenon dynamically illustrated here? [/b]