问题
通过凑微分,如何计算 [$\textcolor{Orange}{\int f(\ln x) \frac{1}{x} \mathrm{d} x}$] ?选项
[A]. $\int$ $f(\ln x) \frac{1}{x}$ $\mathrm{d} x$ $=$ $- \int$ $f(\ln x)$ $\mathrm{d} (\ln x)$[B]. $\int$ $f(\ln x) \frac{1}{x}$ $\mathrm{d} x$ $=$ $\int$ $f(\ln x)$ $\mathrm{d} x$
[C]. $\int$ $f(\ln x) \frac{1}{x}$ $\mathrm{d} x$ $=$ $\int$ $f(\ln x)$ $\mathrm{d} (\ln x)$ $+$ $C$
[D]. $\int$ $f(\ln x) \frac{1}{x}$ $\mathrm{d} x$ $=$ $\int$ $f(\ln x)$ $\mathrm{d} (\ln x)$