**Mark Scheme**

**Working**

*A*,

*B*and

*C*are points on the circumference of a circle, centre

*O*.

*AOB*is a diameter of the circle.

Prove that angle

*ACB*is 90°

You must

**not**use any circle theorems in your proof

**Question**

*A*,

*B*and

*C*are points on the circumference of a circle, centre

*O*.

*AOB*is a diameter of the circle.

Prove that angle

*ACB*is 90°

You must

**not**use any circle theorems in your proof

**[4 marks]**