Q17 of 63 Page 156

In figure, if ∠DAB = 60°, ∠ABD = 50°, then ∠ACB is equal to—

Given ∠DAB = 60° and ∠ABD = 50°


We know that angles in the same segment of a circle are equal.


∴ ∠ADB = ∠ACB


In ΔABD,


By angle sum property,


⇒∠ABD + ∠ADB + ∠DAB = 180°


⇒ 50° + ∠ADB + 60° = 180°


⇒ 110° + ∠ADB = 180°


⇒∠ADB = 180° - 110°


∴ ∠ADB = 70° = ∠ACB

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