Let ABC be an acute angled triangle , and let P and Q be two points on side BC.Construct point C1 in such a way that convex quadrilateral APBC1 is cyclic, QC1||CA, and C1 and Q lie on opposite sides of line AB. Construct point B1 in such a way that convex quadrilateral APCB1 is cyclic, QB1 ||BA, and B1 and Q lie on opposite sides of line AC.Prove that points B1, C1,P and Q lie on a circle.

no idea.anyone?