交换二重积分的次序,得 /()*f2(1)*f3() f1(z)/2(-)dz|/3(t-)dn ∫yA(=10-0r 令=t-u,则=t-, +oO 上式=f(z)f2(-y-)f3(v)dvdz f(z)(t-r)dz=f1(t)*()= f1(1)*[2()*f(O)8 交换二重积分的次序, 得 令v=t−u, 则u=t−v,       + − + − + − + −     = − − −     = −         ( ) ( ) ( )d d ( ) ( )d ( )d ( ) ( ) ( ) 1 2 3 1 2 3 1 2 3 f f u f t u u f f u f t u u f t f t f t ( )  ( ) ( ) ( ) ( )d ( ) ( ) ( ) ( ) ( )d d 1 2 3 1 1 1 2 3 f t f t f t f s t f t s t f f t v f v v =   = − =  =     = − −    + − + − + −    上式   