P,Q,R P, Q, R\,P,Q,R and S S\,S are points on the circumference of a circle with centre MMM.
Prove that the opposite angles PQR PQR\,PQR and PSR PSR\,PSR in the cyclic quadrilateral PQRS PQRS\,PQRS sum to 180∘180^\circ180∘.
