Points PPP, QQQ, R R\,R and S S\,S are points on the circumference of a circle, centre OOO. Chords PQPQPQ, QRQRQR, RSRSRS, and SP SP\,SP are drawn to form a cyclic quadrilateral PQRSPQRSPQRS. Radii OP OP\,OP and OR OR\,OR are drawn.
Angle POR=2y∘POR = 2y^\circPOR=2y∘
Find the size of angle PSRPSRPSR, in terms of yyy. Give reasons for each stage of your working.