SSC CGL 26 Oct 2014 Shift 2 Paper

OA = OB = OC
= Circum – radius
In Δ ABC,
∠ A = 180° – 70° – 40°
= 180° – 110° = 70°
The angle subtended by an arc at the centre is twice to that at the circumference.
∴ ∠ BOC = 2 ∠ BAC
= 2 × 70 = 140°