问题
[$\textcolor{Orange}{\int \csc x \mathrm{d} x}$] 的积分该怎么计算？选项
[A]. $\int$ $\csc x$ $\mathrm{d} x$ $=$ $\ln (\csc x – \cot x)$ $+$ $C$[B]. $\int$ $\csc x$ $\mathrm{d} x$ $=$ $\ln |\csc x – \cot x|$
[C]. $\int$ $\csc x$ $\mathrm{d} x$ $=$ $\ln |\csc x – \cot x|$ $+$ $C$
[D]. $\int$ $\csc x$ $\mathrm{d} x$ $=$ $\ln (\csc x + \cot x)$ $+$ $C$
$$\int \textcolor{Red}{\csc x} \mathrm{d} x =$$ $$\textcolor{Red}{\ln |\csc x – \cot x|} + \textcolor{Yellow}{C}.$$