In the following figure, O is centre of the circle and ΔABC is equilateral.
Find:(i) ∠ADB, (ii) ∠AEB.
Exercise 17 (A) | Q 11 | Page 258
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Since ∠ACBand ∠ADBare in the same segment,
∠ADB = ∠ACB = 60°
Join OA and OB
Here, ∠AOB =2 ∠ACB = 2×60° = 120°
$\angle A E B=\frac{1}{2} \operatorname{Reflex}(\angle AOB )=\frac{1}{2}\left(360^{\circ}-120^{\circ}\right) 120^{\circ}$
(Angle at the centre is double the angle at the circumference subtended by the same chord)
art

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