WAEC - Mathematics (2000 - No. 23)

In the diagram, PQRS is a circle center O. PQR is a diameter and ∠PRQ = 40°. Calculate ∠QSR.

30^o

40^o

45^o

50^o

< Q = < R (OQ = OR = radii)

< QOR = 180° - 2(40°) = 100°

< QSR = < RPQ = \(\frac{1}{2}\) < QOR

= \(\frac{100}{2} = 50°\)