GoGeometry Action 164!

Creation of this resource was inspired by a [url=https://twitter.com/gogeometry/status/1016026193001353217]tweet[/url] posted by [url=https://twitter.com/gogeometry]Antonio Gutierrez[/url] (GoGeometry). [br][br]Below, the [b][color=#38761d]green circle[/color][/b] is tangent to both the [color=#bf9000][b]semicircle[/b][/color] and its [b]diameter[/b]. [br][br]You can move any of the [b]LARGE POINTS[/b] anywhere you'd like [b]AT ANY TIME[/b]. [br][br][b][br]Questions to consider: [br][br][color=#ff00ff]1) What is the measure of the pink angle? How do you know this to be true? [br][/color][/b][br][color=#ff00ff][b]2) How can we formally the phenomenon dynamically illustrated here? [/b][/color][br][br]
Quick (Silent) Demo

Information: GoGeometry Action 164!