Question

极限题目，如图，请问第一步怎么换到第二步的。谢谢大家！

Answer 1

运用了等价无穷小的原理
如图所示

Answer 2

注意：

ln(1 + x) ～ x

ln(x) ～ x - 1

y = (atan(x)/x)^(1/x^2)

y = exp(ln(y))

ln(y) = (ln(atan(x)/x))*(1/x^2)

ln(atan(x)/x) ～ atan(x)/x - 1

ln(y) ～ (atan(x)/x - 1)*(1/x^2)