∫(z)=c0sz-sin cos SIn ∑5, 2n+1 =0 n+ z=O为本性奇点 Reslf(z=l1 1 cos sin   = − 2 2 1 0 0 ( 1) 1 ( 1) 1 ( ) ( ) 2 ! (2 1)! n n n n n n n n     + = = − − = − +   z =  为本性奇点 Re [ ( )] 1 s f z =