Posted by haifeng on 2017-09-09 11:25:55 last update 2017-09-09 11:25:55 | Answers (1) | 收藏
证明函数
\[ f(x)=\begin{cases} x^2, & x \text{为无理数},\\ 0, & x \text{为有理数},\\ \end{cases} \]
仅在 $x=0$ 处有导数.