# Theorem 1.6 Angle at Centre Twice Angle at Circumference

## Instruction

Drag the point B to observe the relationship between and .

## Answer the following questions : (You can drag the points in the figure to help you)

If reflex AOB is , = ____.

If AOB is , = ____.

## The last question gives a proof of Theorem 1.7 Angle in semi-circle

Please note that the converse of Theorem 1.7 is also true.