JAMB - Mathematics (1979 - No. 45)

In the figure, PQ and QR are chords of the circle PQR. QRS is a straight line and PR is equal to RS, < PSR is 20o. What is the size of <POQ.

70^o

90^o

80^o

40^o

60^o

Isosceles Triangle PSR:

RSP ≡ RPS → 20º

That is PRQ = 40º

POQ = 2 * 40 = 80º (Angle subtended by chord PQ at centre is twice angle subtended at circumference).

The size of POQ = 80º