当x=0时, ∫"(0)=lim (0+h)-ln(1+0) =1. h→07 ∫(0)=li n1+(0+)l-ln(1+0) in h→0 h ∫'(0)=1 1,x≤0 ∫(x) :’x>0 上页当x = 0时, h h f h (0 ) ln(1 0) (0) lim 0 + − +  = → − − = 1, h h f h ln[1 (0 )] ln(1 0) (0) lim 0 + + − +  = + → + = 1,  f (0) = 1. . , 0 1 1 1, 0 ( )      +    = x x x f x