于是F(z+A)-F(a)=f5)d5, 因为∫tfed5=fe∫td5=fa)Az, 所以 F(a+△z-F②-f() △z (- B &V)-feIac 2:44:26于是 ( ) ( ) F z z F z +  − = ( )d ,  z+z z f   ( )d z z z f z  +  = 因为   z+z z f (z) d = f (z)z, B z K z + z  0 z •  ( ) ( ) ( ) F z z F z f z z +  − −  所以 ( )d ( ) 1 f f z z z z z −  =  +   [ ( ) ( )]d 1 f f z z z z z −  =  +