O is center of circle C1 and AB is diameter of circle C2. Quadrilateral PQRS is inscribed in the circle with centre O. Find angle QRS.

AngleQRS+ang.QPS=180°(sum of opp.ang .of cyclic quad.is180°)Ang.QRS=180°-ang.QPS =180°-ang.QOS/2(angle subtended by an arc at any part of circle is half the angle sub. by it at any part) =180°-90°/2(angQOS=90°;angle in a semicircle) =180°-45° =135°

AngleQRS+ang.QPS=180°(sum of opp.ang .of cyclic quad.is180°)Ang.QRS=180°-ang.QPS =180°-ang.QOS/2(angle subtended by an arc at any part of circle is half the angle sub. by it at centre) =180°-90°/2(angQOS=90°;angle in a semicircle) =180°-45° =135°