More of those dreaded circles

Yup, another circle question and it seems as though the question list is never-ending. Well, I'm stuck. Again... but here goes

TA and TB are tangents to the circle. C is a point on the circle. P, Q and R are the feet of the perpendicular from C to the three sides of triangle ABT

a) Name three groups of concyclic points (got this)

b) hence show that angle CRQ = angle CQP and angle CQR = angle CQP

c) if QC = 9cm and PC = 10cm, find CR.

http://img168.imageshack.us/img168/6955/43696800si4.png

Any help appreciated!