A, B and C are the three points on a circle such that ∠ABC = 35° and ∠BAC = 85°. What is the angle (in degrees) subtended by arc AB at the centre of the circle?
A60
B90
C135
D120
Answer:
D. 120
Read Explanation:
In triangle ABC,
∠A + ∠B + ∠C = 180 (angle sum property)
∠C = 180 - ∠A - ∠B = 180° – 35° – 85° = 60°
∠ AOB = 2∠ACB (Angle subtended at centre is twice that on circle)
