例2x1=0.3c0(x1) x2=0.4cos(rt+ 37)=0.4c0(兀t-) x2超前x13x1超前x2z (-2≤≤+2m) 图6-410 例2 x1 =0.3cos( t ) x2 =0.4cos( t ) 2 3 + x2 超前 x1 2 3 =0.4cos( t ) 2  − x1 超前 x2 2  1 2 图6-4 (−2   +2)