In the diagram, KS is a tangent to the circle centre O at R and ∠ROQ = 80º. Find ∠QRS.
- 90o
- 80o
- 50o
-
40o
The correct answer is: D
Explanation
QOP = 180 - 100(straight line angle) → 80°
OPQ and OQP are isosceles of 40° each.
∠QRS = ∠RPQ (theorem: angle in the alternate segment are equal)
∠RPQ = 40º
∠QRS = 40º