Angle at centre is twice the angle at the circumference

Blue pt for : Moving the respective point A, B and C along the circumference. Slide for: Changing the radius of the circle. Exploration: 1. Move pt A, B or C. (Hint: Select pt C and move pt C to the extreme left or right) 2. Use a table to organise the data collected from the observation of the angles demonstrated. 3. Find the related angles and the findings from the exploration and show the angle property of circle - Angle in a semi-circle is a right angle.