Let X and Y be the diameter's extremes of a circunference Γ and N be the midpoint of one of the arcs XY of Γ. Let A and B be two points on the segment XY. The lines NA and NB cuts Γ again in C and D, respectively. The tangents to Γ at C and at D meets in P. Let M the the intersection point between XY and NP. Prove that M is the midpoint of the segment AB. geometrypower of a pointradical axisgeometry proposed