Question:
In figure, O is the centre of the circle. Find ∠BAC.
Solution:
We have ∠AOB = 80°
And ∠AOC = 110°
Therefore, ∠AOB + ∠AOC + ∠BOC = 360° [Complete angle]
⇒ 80° + 100° + ∠BOC = 360°
⇒ ∠BOC = 360° − 80° − 110°
⇒ ∠BOC = 170°
By degree measure theorem
∠BOC = 2∠BAC
⇒ 170° = 2∠BAC
⇒ ∠BAC = 170°/2 = 85°