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JAMB Mathematics 1997 Question 25

Question 25

Circle Theorems

Each of the base angles of an isosceles triangle is 58° and all the vertices of the triangles lie on a circle. Determine the angles which the base of the triangle subtends at the centre of the circle.

  1. A.128°
  2. B.116°
  3. C.64°
  4. D.58°
Show the answer and explanation

Answer: A (128°)

Explanation

The apex angle is 180° − 2(58°) = 64°. The angle at the centre is twice the angle at the circumference, so 128°.