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WAEC Mathematics 2002 Question 30

Question 30

Circle Theorems

In the diagram. O is the centre of the circle. Which of the following is/are not true? I. a = b II. b + c = 180° III. a + b = c

Diagram for this question
  1. A.I and II only
  2. B.II and III only
  3. C.II only
  4. D.III only
Show the answer and explanation

Answer: D (III only)

Explanation

An angle in a semicircle is 90°, so a = b = c = 90°. Then a = b and b + c = 180° are true, but a + b = 180° ≠ c, so only III is not true.