AB is a chord of a circle with centre O. C is a point on the circumference of the circle in the minor sector. If ∠ABO = 40°, what is the measure (in degree) of ∠ACB?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 130°
In the given figure, ∠ABO = ∠BAO (Angles made by the radius on the same chord are equal)
In tri(AOB), ∠ABO + ∠BAO + ∠AOB = 180º
∠AOB = 180 - (40 + 40) = 180 - 80 = 100º
External ∠AOB = 360 - 100 = 260º
∠ACB = (1/2) × 260 = 130º