📝 题目
解 用分部积分法得
$$ {\int }_{0}^{\pi }x\sin x\mathrm{\;d}x = - {\left. x\cos x\right| }_{0}^{\pi } + {\int }_{0}^{\pi }\cos x\mathrm{\;d}x = \pi . $$
💡 答案与解析
解 用分部积分法得
$$ {\int }_{0}^{\pi }x\sin x\mathrm{\;d}x = - {\left. x\cos x\right| }_{0}^{\pi } + {\int }_{0}^{\pi }\cos x\mathrm{\;d}x = \pi . $$