Creation of this resource was inspired by a [url=http://gogeometry.com/school-college/4/p1339-circle-diameter-tangent-secant-parallelogram.htm]problem[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br]You can move any of the [color=#bf9000][b]LARGE YELLOW POINTS[/b][/color] anywhere you'd like AT ANY TIME. [br][br]Without referencing the problem in another browser tab, how would you describe this phenomenon? [br]That is, how would you put what you see into words? [br][br][b][color=#ff00ff]How can we formally prove what is dynamically illustrated here? [/color][/b]