形式解 (4)=/(t)2 7(4)=e iHt/y Bt Bt do·Sih 2uc 之L Bt Bt COS Sn lc Llc B+iB Bt SIn Lc形式解             + + = = +  =  = − c e Bt B B iB c e Bt B B i c e Bt c e Bt i n c e Bt U t e t U t iHt i        2 sin 2 sin 2 cos 2 sin 2 cos ( ) ( ) ( ) 2 1 3 /   