GoGeometry Action 164!
Creation of this resource was inspired by a tweet posted by Antonio Gutierrez (GoGeometry).
Below, the green circle is tangent to both the semicircle and its diameter.
You can move any of the LARGE POINTS anywhere you'd like AT ANY TIME.
Questions to consider:
1) What is the measure of the pink angle? How do you know this to be true?
2) How can we formally the phenomenon dynamically illustrated here?