[Unl(m)+-n4(on)]=0 丌 u(t)cos katd(ot) nT Jo (m cos katd(ot)+ Um coS katd(at) sin kot sin kot=c k k 丌 u(t)sin katd(ot) 丌0 2丌 Um sin katd(at )+ JO U sin kotd(at) ( ) ( )  0 2 1 2 0 0 = + − =   U d t U d t m  m             = + − = = − = = + − =       sin ( ) sin ( ) 1 ( )sin ( ) 1 sin sin 0 cos ( ) 1 cos ( ) 1 ( )cos ( ) 1 2 0 0 2 0 2 0 2 0 0 2 0 U k t d t U k t d t b u t k t d t k t k U k t k U U k t d t U k t d t a u t k t d t m m k m m m m k                              