积分号xlnx/(1+x^2)^2

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积分号xlnx/(1+x^2)^2

分部积分啦!
∫xlnx/[(1+x^2)^2]dx
=(-1/2)∫lnxd(1/(1+x^2))
=(-1/2)lnx/(1+x^2)+(1/2)∫1/[(1+x^2)*x]dx
=(-1/2)lnx/(1+x^2)+(1/2)∫x/[(1+x^2)*x^2]dx
=(-1/2)lnx/(1+x^2)+(1/4)∫1/[(1+x^2)*x^2]d(x^2)
=(-1/2)lnx/(1+x^2)+(1/4)∫[1/x^2-1/(1+x^2)]d(x^2)
=(-1/2)lnx/(1+x^2)+(1/4)[ln(x^2)-ln(1+x^2)]+C
=(-1/2)lnx/(1+x^2)+(1/4)ln[x^2/(1+x^2)]+C