例:正猴余猴信号的拉氏变换 cos at sin at ot J Jot e f(1)=l(1) e te F(S)=( S+jo S-jo S+jo s-j@ 2 S2+0 S2+0例： 正弦余弦信号的拉氏变换 2 ( ) ( ) j t j t e e f t u t  −  + = 2 2 2 1 ) 1 1 ( ) (    + = − + + = S S S j S j F S j e e f t u t j t j t 2 ( ) ( )  −  − = 2 2 2 1 ) 1 1 ( ) (     + = − + + − = S S j S j j F S cost sint