ABCD is a cyclic quadrilateral. The lines AD and BC meet at X, and the lines AB and CD meet at Y . The line joining the midpoints M and N of the diagonals AC and BD, respectively, meets the internal bisector of angle AXB at P and the external bisector of angle BYC at Q. Prove that PXQY is a rectangle geometryrectangleangle bisectorcyclic quadrilateralCyclic