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Question
In the following figure, O is centre of the circle and ΔABC is equilateral.
Find:
- ∠ADB,
- ∠AEB.
Solution
Since ∠ACB and ∠ADB are in the same segment,
∠ADB = ∠ACB = 60°
Join OA and OB
Here, ∠AOB = 2∠ACB
= 2 × 60°
= 120°
`∠AEB = 1/2 "Reflex" (∠AOB) = 1/2 (360^circ - 120^circ) = 120^circ`
(Angle at the centre is double the angle at the circumference subtended by the same chord)
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