We have, ∠BOC = 30° and ∠AOB = 60°

∠AOC = ∠AOB + ∠BOC = 60° + 30° = 90°

We know that angle subtended by an arc at the centre of a circle is double the angle subtended by the same arc on the remaining part of the circle.

∴ 2∠ADC = ∠AOC

⇒ ∠ADC = 1/ 2 ∠AOC = 1/ 2 × 90°

⇒ ∠ADC = 45° **Ans**