Let ABC be an acute triangle with AB<AC<BC inscribed in a circle (c) and let E be an arbitrary point on its altitude CD. The circle (c1) with diameter EC, intersects the circle (c) at point K (different than C), the line AC at point L and the line BC at point M. Finally the line KE intersects AB at point N. Prove that the quadrilateral DLMN is cyclic. geometryCyclicConcycliccircles