passwella.
Menu

WAEC Mathematics 2017 Question 19

Question 19

Circle Theorems

The diagram shows a circle centre O. If ∠STR = 29° and ∠RST = 46°, Calculate the value of ∠STO.

Diagram for this question
  1. A.12°
  2. B.15°
  3. C.29°
  4. D.34°
Show the answer and explanation

Answer: B (15°)

Explanation

∠ROT = 2 × ∠RST = 92° (angle at centre). Triangle ROT is isosceles, so ∠RTO = (180° − 92°)/2 = 44°. ∠STO = 44° − 29° = 15°.