Draw the figure according to the question.
Triangle OPQ is an isosceles triangle. OP and OQ being the radius. Angle OPQ =Angle OQP.
Let them be x degrees.
Angle TPO= angle TQO =90 degrees
Angle TPQ=angle TQP=90-x
In triangle TPQ
Angle PTQ=180-(90-x+90-x) (by angle sum property )
On solving angle PTQ=2x=2 angle OPQ