°E-(曲线 E-x曲线 EAP 0 4 Eat E,E变化频率为x的2倍 T 2T E,E彼此变化步调相反 x=A cos(at+oo) kA'coS(Ot+o) k= kAsin(ot+o)E- t曲线 E- x 曲线 E k , E p变化频率为x 的 2 倍 E k , E p彼此变化步调相反 Ep Ek EA A x E kA ( t ) 0 2 2 k sin 21 =  +  x tt T T/2 E E E p E k T  2 T  E kA ( t ) x A ( t ) 0 2 2 p 0 cos 21 cos     = + = +