In this illustration, instead of showing students the obvious symmetry properties of circle, the students are instead requested to prove themselves are the property. While some students are able to observe and prove effectively, most students may required scaffold from teacher:
1. Upon selecting "Show radius", do you observe the two triangles, triangle OCY and triangle ODY?
2. For each triangle, are you able to able to find all the sides?
3. What do you notice about YC and YD?
