P is a point in side a convex quadrilateral such that[PAB]=[PBC]=[PCD]=[PDA].Prove that P is the midpoint of either AC or BD.

Problema 4.[25 pts] P is a point inside a convex quadrilateral such that [PAB] = [PBC] = [PCD] = [PDA]. Prove that P is the midpoint of either AC or BD. B A P D