X XXXxXXxx Oxxxxxxxxxx XXXXXXXXXXX L d 2 1eEL J2=dtnb ee Ld 2 I eEL ee Ld y=Vity 2 m e 02 e 0 2 e 0 1 2 21 v v Ld m L eE m eE y y y +   = + = 2 e 0 2 tan v Ld m eE y = d  = 2 e 0 2 1 21 21   = = vL m eE y at p 12 p L d +- 1 y2 y o y x v0  