问题
[$\textcolor{Orange}{\int \frac{1}{\sin ^{2} x} \mathrm{d} x}$] 的积分该怎么计算？选项
[A]. $\int$ $\frac{1}{\sin ^{2} x}$ $\mathrm{d} x$ $=$ $- \cot x$ $+$ $C$[B]. $\int$ $\frac{1}{\sin ^{2} x}$ $\mathrm{d} x$ $=$ $- \cos x$ $+$ $C$
[C]. $\int$ $\frac{1}{\sin ^{2} x}$ $\mathrm{d} x$ $=$ $\cot x$ $+$ $C$
[D]. $\int$ $\frac{1}{\sin ^{2} x}$ $\mathrm{d} x$ $=$ $- \cot x$
$$\int \textcolor{Red}{\frac{1}{\sin ^{2} x}} \mathrm{d} x =$$ $$\textcolor{Red}{- \cot x} + \textcolor{Yellow}{C}.$$