oO 我们也可以用此S=(O)m=」 sin at sin at F(o=If(te yo dt Jat r1 2a sin at e o dt=u(o+a-u(o-a)l 2 at 当0=0时 ∞ F(==f(Odt=sa -d Sa=F(jol O=0我们也可以用此来求 dt t at S f t dt a   + − + − = = sin ( ) [ ( ) ( )] 2 sin 2 1 sin ( ) ( ) e dt u a u a at a at e dt t at F j f t e dt j t j t j t = = + − − = = − + − − + − + − −           当  = 0 时       = = = = = + − =  0 0 ( ) ( ) ( ) S F j F j f t dt S a a −a a  