Q11 of 69 Page 9

In a Δ ABC, If ∠A = 60°, ∠B =80° and the bisectors of ∠B and ∠C meet at O, then ∠BOC=

In

∠A + ∠B + ∠C = 180o


60o + ∠B + ∠C = 180o


∠B + ∠C = 120o


∠B + ∠C = 60o (i)



∠BOC + ∠OBC + ∠OCB = 180o


∠BOC + ∠B + ∠C = 180o


∠BOC + (∠B + ∠C) = 180o


∠BOC + 60o = 180o [From (i)]


∠BOC = 120o

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