f(x)=ln[(1+x)/(1-x)]定义域为(1+x)/(1-x)>0 ==> (x+1)/(x-1)<0 ==> -1<x<1——是对称区间所以,f(-x)=ln[(1-x)/(1+x)]=-ln[(1+x)/(1-x)]=-f(x)所以,f(x)为奇函数当f(x)=ln[(1+x)/(1-x)]>0即,(1+x)/(1-x)>1==> [(1+x)/(1-x)]-1>0==> [(1+x)-(1-x)]/(1-x)>0==> 2x/(x-1)<0==> 0<x<1