等价无穷小：arcsinx～x,ln(1+x)～x（x→0）所以,x→0时,arcsin(x/√(1-x))～x/√(1-x),ln(1-x)～-x,ln(x+√(1+x^2))＝ln(1+x+√(1+x^2)-1)～x+√(1+x^2)-11、原极限＝lim x/√(1-x) / (-x)＝lim (-1)/√(1-x))＝-12...