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不定积分x乘以arctanxdx怎么求?

题目详情
不定积分x乘以arctanx dx怎么求?
▼优质解答
答案和解析
∫ xarctanx dx
= ∫ arctanx d(x²/2)
= (1/2)x²arctanx - (1/2)∫ x² d(arctanx)
= (1/2)x²arctanx - (1/2)∫ x²/(x² + 1) dx
= (1/2)x²arctanx - (1/2)∫ [(x² + 1) - 1]/(x² + 1) dx
= (1/2)x²arctanx - (1/2)∫ dx + (1/2)∫ dx/(x² + 1)
= (1/2)x²arctanx - x/2 + (1/2)arctanx + C