例:单边正弦、余弦信号的拉氏变换 u(t) cos at u(t)sin at eute e f(0)=0) f()=l(2) F(S)=( F(S)=( S+j@ s-j@ 2 S+jo S-jo 2j S2+ S2+10 例: 单边正弦、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 u(t) cost u(t)sint