Isosceles Triangle
1. If the vertex angle is the center of the circle(point A), how do we know this must be an isosceles triangle?
2. Use the 
to measure the base angles. What can you say about their measures?
3. Drag points B and C. What can you say about the measures of the base angles?
4. Click this 
and slide down to this icon 
to bisect vertex angle A. What can you say about the two triangles that are generated? Why?