Given a cyclic quadriteral ABCD. The circumcenter lies in the quadriteral ABCD. Diagonals AC and BD intersects at S. Points P and Q are the midpoints of AD and BC. Let p be a line perpendicular to AC through P, q perpendicular line to BD through Q and s perpendicular to CD through S. Prove that p,q,s intersects at one point. geometrycircumcircleperpendicular