In the figure, the bisector of B and C meet at O. Then ∠ BOC is
90∘+12∠A
From the given figure,
∠BOC = 180∘−(∠2 + ∠4)
= 180∘ - (∠B2 + ∠C2 )
= 180∘ - (180∘−∠A2)
[∵ 180∘ - ∠ A = ∠ B + ∠ C]
= 180∘ - 90∘ + ∠A2
= 90∘ + ∠A2