P R and S lie on a circle centre O as shown in ... - JAMB Mathematics 2004 Question

P, R and S lie on a circle centre O as shown in the diagram while Q lies outside the circle. Find < PSO

< PRS = 20^o + 35^o = 55^o

< POS = 2 < PRS

2 x 55^o = 10^o

< OPS = < PSO = x

In (\bigtriangleup)POS

OP = OS(radii)

(\bigtriangleup)POS is an isosceles

2x + 110^o = 180^o

2x = 180^o - 110^o = 70^o

x = (\frac{70^o}{2})

= 35^o