Jix+vx2-1(e+e")Idy Ix+iv1-x cosy]dy P() P(-1)=(-1)(1) 1 P1  l P( 1) ( 1) 1         x x e e d i i l       0 2 ( )] 2 1 [ 1 1     x i x d l [ 1 cos ] 1 2 0    