L证明: P()=「W(t,o)lO 『。* s(t-ts(t+te o dido 2兀 2 2 s(a-1 ts(t+to(rdt = s(t证明： * * 2 ( ) ( , ) 1 1 1 ( ) ( ) 2 2 2 1 1 ( ) ( ) ( ) 2 2 | ( ) | j P t W t d s t s t e d d s t s t d s t              − = − + = − + =    ＝