$$$\frac{1}{\sin^{2}{\left(x \right)}}$$$ 的积分

求$$$\int \frac{1}{\sin^{2}{\left(x \right)}}\, dx$$$。

将被积函数用余割表示:

$${\color{red}{\int{\frac{1}{\sin^{2}{\left(x \right)}} d x}}} = {\color{red}{\int{\csc^{2}{\left(x \right)} d x}}}$$

$$$\csc^{2}{\left(x \right)}$$$ 的积分为 $$$\int{\csc^{2}{\left(x \right)} d x} = - \cot{\left(x \right)}$$$:

$${\color{red}{\int{\csc^{2}{\left(x \right)} d x}}} = {\color{red}{\left(- \cot{\left(x \right)}\right)}}$$

因此，

$$\int{\frac{1}{\sin^{2}{\left(x \right)}} d x} = - \cot{\left(x \right)}$$

加上积分常数：

$$\int{\frac{1}{\sin^{2}{\left(x \right)}} d x} = - \cot{\left(x \right)}+C$$

$$$\int \frac{1}{\sin^{2}{\left(x \right)}}\, dx = - \cot{\left(x \right)} + C$$$A