In the diagram PX is a tangent to the circle an... - WAEC Mathematics 2008 Question

(\bigtriangleup) RST is equilateral triangle, hence

< TRS = < RTS = < RSt = 60^o

But < PTR = 60^o(Angle between a chord and a tangent at the point of contact = Angle in the alt. segment). From the diagram < PTS = < PTR + < RTS

= 60^o + 60^o = 120^o