P,Q,R,S,T are points on a circle with centre O so that ∠PTQ= 2 x ∠RTS and PQ is parallel to RS. If P,O,Q are in a straight line, then the value of ∠SOQ is
∠PTQ= 90 (angle in a semi circle)
Hence ∠RTS = 45.
∠ROS = 90 ( Inscribed angle= 2 ×Angle at circumference)
OR=OS=OR (radius)
∠RSO = ∠SOQ= 45∘ (interior alternate angles)