Posted by haifeng on 2022-03-16 21:51:22 last update 2022-03-16 22:03:10 | Answers (0) | 收藏
求
\[\int_{\frac{\pi}{4}}^{\frac{\pi}{2}}\csc^4 x\mathrm{d}x\]
[Hint] 将被积函数拆成 $\csc^2 x\cdot\csc^2 x$, $\csc^2 x\mathrm{d}x=-\mathrm{d}\cot x$. 然后用分部积分.
