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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.
Solution
OABC is a cyclic quadrilateral
∴ ∠AOB + ∠ACB = 180°
(Pair of opposite angles in a cyclic quadrilateral are supplementary)
`=>` ∠ACB = 180° – 2a°
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