Prove that there can be only one perpendicular from a given point to a given line. (Hint:...

Prove that there can be only one perpendicular from a given point to a given line. (Hint: Can a triangle ∆ABC have two right angles, say at B and C ? Locate D on the opposite side of line as A so that BA = BD and m∠ABC = m∠CBD. What can be proven from this figure to get a contradiction?)