Description for Correct answer:


\( \Large \angle BOC = 2 \times 50 ^{\circ} = 100 ^{\circ} \)

In \( \Large \triangle OBC, OB = OC \)

=> \( \Large \angle OBC = \angle OCB \)

\( \Large \therefore Sum\ of\ three\ angles\ of\ a\ triangle = 180 ^{\circ} \)

=> \( \Large \angle OBC + \angle OCB + \angle BOC = 180 ^{\circ} \)

=> \( \Large 2 \angle OBC + 100 ^{\circ} = 180 ^{\circ} \)

-> \( \Large \angle OBC = \frac{80 ^{\circ} }{2} = 40 ^{\circ} \)