Question:

Let ABCD be a convex quadrilateral, I1 and I₂ be the

Last updated: 7/11/2022

Let ABCD be a convex quadrilateral, I1 and I₂ be the

Let ABCD be a convex quadrilateral, I1 and I₂ be the incenters of ΔABC and ΔDBC respectively. The line I1I₂ intersects the lines AB and DC at the points E and F respectively. Suppose lines AB and DC intersect at P, and PE = PF. Prove that the points A, B, C, D are concyclic.