limx→0√1+x−1log(1+x)
=limx→0(√1+x−1)(√1+x+1)log(1+x)(√1+x+1)
=limx→0xlog(1+x)(√1+x+1)
=limx→01log(1+x)x×limx→01(√1+x+1)
=1×12=12