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Here is what I have done

\begin{align} &\int_0^1\frac{\ln(x)\ln(1+x^2)}{1-x}dx\\ =&\int_0^1\frac{(1+x)(1+x^2) \log(x)\log(1-x^4)}{1-x^4} \ dx\\ &-\int_0^1\frac{(1+x)\log(x)\log(1-x^2)}{1-x^2} \ dx \end{align} and, then, after letting $x^4\mapsto x$ and $x^2\mapsto x$ respectively, use the beta function. Similarly we proceed with the second twin and we are done.

Please teach me another ways that only use real analysis.

Above also answers the first integral here

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  • You may find this interesting http://math.stackexchange.com/questions/524358/evaluating-int-01-frac-log-x-log-left1-x4-right1x2dx – Bennett Gardiner Nov 10 '14 at 12:12
  • @BennettGardiner you may use there the same technique I show here. – user 1591719 Nov 10 '14 at 12:18
  • @BennettGardiner The valid solutions there seem to get reduced to the same beta story function, sooner or later. I'd like something else, a revolutionary approach, some different ideas. – user 1591719 Nov 10 '14 at 12:25

1 Answers1

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Denote $K_{\pm} = \int_0^1 \frac{\ln t}{1\pm t}dt$ and integrate the twins as follows \begin{align} I_\pm =&\int_0^1\frac{\ln x\ln(1+x^2)}{1\pm x}dx \\ =& \int_0^1 \ln(1+x^2)\> d\left(\int_0^x \frac{\ln t}{1\pm t}dt\right)\\ =& \>\ln2 \int_0^1 \frac{\ln t}{1\pm t}dt -\int_0^1 \frac{2x}{1+x^2}\left(\int_0^x \frac{\ln t}{1\pm t}\overset{t=xy}{dt}\right)dx\\ =& \>\ln2 K_{\pm}-2\int_0^1 \int_0^1\frac{x^2\ln(xy)}{(1+x^2)(1\pm xy)}dy\>dx\\ =& \>\ln2 K_{\pm} + 2\int_0^1 \int_0^1\frac1{1+y^2} \bigg( \frac{(1\mp xy)\ln(xy)}{1+x^2} -\frac{\overset{t=xy}{\ln(xy)}}{1\pm xy} \bigg)dx\>dy\\ =& \>\ln2 K_{\pm} \pm 2\int_0^1 \frac{x\ln x}{1+x^2} \overset{x^2\to x}{dx}\int_0^1\frac {2y}{1+y^2}dy\\ &+ 4\int_0^1 \frac{\ln x}{1+x^2} dx\int_0^1\frac 1{1+y^2}dy-\int_0^1 \frac{2}{y(1+y^2)}\left(\int_0^y \frac{\ln t}{1\pm t}dt\right) dy\\ = & \>\ln2 K_{\pm} \pm 2\left(\frac14K_+\right)\ln2 +4\>(-G)\>\frac\pi4 - \int_0^1 d\left(\ln\frac{y^2}{1+y^2}\right)\int_0^y \frac{\ln t}{1\pm t}dt\\ =& \>2\ln2 K_{\pm}\pm \frac12 \ln2 K_+ -\pi G+2\int_0^1 \frac{\ln^2y}{1\pm y}-I_{\pm}\\ \end{align} Substitute $K_- =-\frac{\pi^2}6$, $K_+ =-\frac{\pi^2}{12}$, $\int_0^1 \frac{\ln^2y}{1-y}dy=2\zeta(3)$, $\int_0^1 \frac{\ln^2y}{1+y}dy=\frac32\zeta(3)$ into above expression to arrive at \begin{align} &I_-=\int_0^1\frac{\ln x\ln(1+x^2)}{1-x}dx = -\frac{3\pi^2}{16}\ln2-\frac\pi2 G+2\zeta(3)\\ &I_+=\int_0^1\frac{\ln x\ln(1+x^2)}{1+x}dx =-\frac{\pi^2}{16}\ln2-\frac\pi2 G+\frac32\zeta(3) \end{align}

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