Problem: In triangle ABC,AB=AC, angle A=40∘. Point O is within the triangle with angle OBC= angle OCA. The number of degrees in angle BOC is:
Answer Choices:
A. 110
B. 35
C. 140
D. 55
E. 70
Solution:
∠BOC=180−21(∠B+∠C). But 21(∠B+∠C)=21⋅140=70. ∴∠BOC=110 (degrees).