(c)单边余弦信号 cOS.(t) LIcos Oota(t)=ll(eo te o)e(t) ]= 2 S-jOo S+jOo 5+@ 即 cos Ota()< S-+( c ) 单边余弦信号 cos ( ) 0  t t ( ) ( )] 2 1 [cos ( )] [ 0 0 0 L t t L e e t j t j t     −  = + 2 0 2 0 0 ] 1 1 [ 2 1   + = + + − = s s s j s j 2 0 2 0 cos ( )    +  s s 即 t t