Question

The figure shows two circles which intersect at A and B. The centre of the smaller circle is O and lies on the circumference of the larger circle. Given that ∠APB = a°.

Calculate, in terms of a°, the value of : ∠ACB,

Give reasons for your answers clearly.

Answer 1

OABC is a cyclic quadrilateral

∴ ∠AOB + ∠ACB = 180° 

(Pair of opposite angles in a cyclic quadrilateral are supplementary)

`=>` ∠ACB = 180° – 2a°