QQuestion
AB is a diameter of a circle with centre O. If the chord AC subtends ∠60° at the centre then value of ∠OCB is
(a) 20°
(b) 30°
(c) 40°
(d) 50°
✓Answer
(b) 30°
Explanation:
In a circle, the angle subtended by a chord at the centre is twice the angle subtended at the circumference.
Given ∠AOC = 60°, the angle at the circumference ∠OCB is:
∠OCB = 60° \over 2 = 30°
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