Q6 of 69 Page 9

In Δ ABC, if bisectors of ∠ABC and ∠ACB intersect at O angle of 120°, then find the measure of ∠A.

In

∠BOC + ∠OBC + ∠OCB = 180o


120o + ∠B + ∠C = 180o


(∠B + ∠C) = 60o


∠B + ∠C = 120o (i)


In


∠A + ∠B + ∠C = 180o


∠A + 120o = 180o [From (i)]


∠A = 60o


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State exterior angle theorem.

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