ABC is a triangle with a right angle at  A.M and N are points on BC such that AM is the altitude, and AN is the  angle bisector of ∠BAC. If CN/NB=21,what is CM/MB? In a triangle ABC, the altitudes from A,B, C meet BC,AC and AB at D,E, F.Prove that perpendicular bisector of EF also bisects BC.How to prove it?