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In the adjoining figure, ABCD is a cyclic quadrilateral in which ∠BCD = 100° and ∠ABD = 50°. Find ∠ADB. |
Answer» It is given that ABCD is a cyclic quadrilateral We know that the opposite angles of a cyclic quadrilateral are supplementary So we get ∠A + ∠C = 180o By substituting the values ∠A + 100o = 180o On further calculation ∠A = 180o – 100o By subtraction ∠A = 80o Consider △ ABD Using the angle sum property ∠A + ∠ABD + ∠ADB = 180o By substituting the values 80o + 50o + ∠ADB = 180o On further calculation ∠ADB = 180o – 80o – 50o By subtraction ∠ADB = 180o – 130o So we get ∠ADB = 50o Therefore, ∠ADB = 50o. |
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