Creation of this applet was inspired by a [url=http://www.gogeometry.com/school-college/p939-circle-tangent-parallel-secant-midpoint.htm]problem[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br]You can move any of the [b]LARGE POINTS[/b] anywhere you'd like [b]AT ANY TIME[/b]. [br][br][i]How would you describe the phenomena you see in words?[/i] [br][br][b][color=#0000ff]How can we formally prove what is dynamically illustrated here? [/color][/b]