**Helpful Links****Question**

11)

*A*and

*B*are points on a circle, centre

*O*.

*BC*is a tangent to the circle.

*AOC*is a straight line.

Angle

*ABO*=

*x*°.

Find the size of angle

*ACB*, in terms of

*x*.

Give your answer in its simplest form.

Give reasons for each stage of your working.

**[5 marks]**