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In figure, if ∠OAB = 40°, then ∠ACB equals(a) 50°(b) 40°(c) 60°(d) 70° |
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Answer» Answer is (a) 50° ∵ OA = OB (radius of circle) ∴ ∠OAB = ∠OBA (angles opposite to equal sites) ⇒ ∠OBA = 40° In right angled ∆OAB ∠OAB + ∠OBA + ∠AOB = 180° ⇒ 40° + 40° + ∠AOB = 180° ⇒ ∠AOB = 180° – 80° ⇒ ∠AOB = 100° We know that ∠ACB = \(\frac { 1 }{ 2 }\)∠AOB = \(\frac { 1 }{ 2 }\) x 100° = 50° |
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