(b) Find f'(x) if f(x) = [tan-1(x)]2. 15. A ladder 10 ft long leans against a vertical wall. If the bottom of the ladder slides Vertical Wall Ladder of length 10 ft Ladder sliding away h from wall at 2 ft/s speed Floor away from the base of the wall at a speed of 2 ft/sec, how fast is the angle 0 between the ladder and the wall changing when the bottom of the ladder is 6 ft from the base of the wall