In the given figure, find ∠ADC.

Given: ∠AOB = 60^o  and  ∠BOC = 30^o

∠AOC = ∠AOB + ∠BOC

⇒ ∠AOC = 60^o + 30^o

⇒ ∠AOC = 90^o 

We know that the angle subtended by an arc at the centre is twice the angle subtended by it at any other point on the circle.

∴ ∠AOC = 2∠ADC

⇒ 2∠ADC = 90^o    [∵ ∠AOC = 90^o ]

⇒ ∠ADC = 45^o

Hence, the value of ∠ADC is 45^o.