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In Fig. if PR is tangent to the circle at P and Q is the centre of the circle, then ∠POQ =A. 110° B. 100° C. 120° D. 90° |
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Answer» Answer is C. 120° Given: ∠RPQ = 60° Property 1: The tangent at a point on a circle is at right angles to the radius obtained by joining center and the point of tangency. Property 2: Sum of all angles of a triangle = 180°. By property 1, ∆OPR is right-angled at ∠OPR (i.e., ∠OPR = 90°). OP = OQ [∵ radius of circle] ∴ ∠OPQ = ∠OQP = 30° Now by property 2, ∠OPQ + ∠OQP + ∠POQ = 180° ⇒ 30° + 30° + ∠POQ = 180° ⇒ 60° + ∠POQ = 180° ⇒ ∠POQ = 180° - 60° ⇒ ∠POQ = 120° Hence, ∠POQ = 120° |
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