from Del Hawley
The three corners of a triangle are sitting on a circle. The angles are called Angle A, Angle B and Angle C. The dot in the middle of the circle shows the centre. The counter is measuring the size of Angle A in degrees.
What is the smallest Angle A can be?
What is the largest Angle A can be?
What else do you notice about Angle A as you move the corners of the triangle around the circle?
This problem is interactive, which means that you can move parts of the picture around and see what happens. Just click and drag the corners of the triangle.