对 $\int$ $f(\tan x) \sec ^{2} x$ $\mathrm{d} x$ 凑微分的计算方法(B006)

问题

通过凑微分,如何计算 [$\textcolor{Orange}{\int f(\tan x) \sec ^{2} x \mathrm{d} x}$] ?

选项

[A].   $\int$ $f(\tan x) \sec ^{2} x$ $\mathrm{d} x$ $=$ $\int$ $f(\tan x)$ $\mathrm{d}$ $(\tan x)$

[B].   $\int$ $f(\tan x) \sec ^{2} x$ $\mathrm{d} x$ $=$ $- \int$ $f(\tan x)$ $\mathrm{d}$ $(\tan x)$

[C].   $\int$ $f(\tan x) \sec ^{2} x$ $\mathrm{d} x$ $=$ $\int$ $f(\tan x)$ $\mathrm{d}$ $(\cot x)$

[D].   $\int$ $f(\tan x) \sec ^{2} x$ $\mathrm{d} x$ $=$ $\int$ $f(\tan x)$ $\mathrm{d} x$



显示答案

$$\int \textcolor{Red}{f(\tan x)} \textcolor{Green}{\times} \textcolor{Red}{\sec ^{2} x} \mathrm{d} \textcolor{Yellow}{x} =$$ $$\int \textcolor{Red}{f(\tan x)} \mathrm{d} (\textcolor{Yellow}{\tan x}).$$

常用的几种凑微分形式: