问题描述: 已知f(x)的一个原函数为xsinx,求∫xf('x)dx是求∫xf'(x)dx 括号错了! 1个回答 分类:数学 2014-11-17 问题解答: 我来补答 ∵ ∫f(x)dx = xsinx + c [Given,已知]∴ f(x) = sinx + xcosx [Derivative,求导]∴ ∫xf'(x)dx = ∫xdf(x) [Completing differentiation,凑微分]= xf(x) - ∫f(x)dx + c [Integration by parts,分部积分]= x(sinx + xcosx) - xsinx + c [Substitution,代入]= x²cosx + c [Simplification,化简] 展开全文阅读