P,Q P, Q\,P,Q and R R\,R lie on the circumference of a circle with centre OOO. POR POR\,POR is a diameter.

Prove that ∠PQR=90∘\angle PQR = 90^\circ∠PQR=90∘
You must not use any circle theorems in your proof.
Practise Eduqas GCSE Maths Proof of the Circle Theorems with exam-style questions for Foundation and Higher tier. 20 questions, matched to the Eduqas GCSE Maths (C300QS) specification and written in Component 1 and Component 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.