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$\ds{\int_{0}^{1}
{\ln\pars{1 + x \a más de 1 - x} \over x\raíz{1 - x^{2}}}\,\dd x
={\pi^{2} \over 2}:\ {\large ?}}$
Con $\ds{x \equiv \cos\pars{\theta}}$:
\begin{align}&\color{#c00000}{\int_{0}^{1}%
\ln\pars{1 + x \over 1 - x}\,{\dd x \over x\root{1 - x^{2}}}}
=\int_{\pi/2}^{0}
\ln\pars{1 + \cos\pars{\theta} \over 1 - \cos\pars{\theta}}\,
{-\,\dd\theta \over \cos\pars{\theta}}
\\[3mm]&=-2\int_{0}^{\pi/2}{\ln\pars{\tan\pars{\theta/2}} \over \cos\pars{\theta}}\,\dd\theta
\end{align}
Set $\ds{\tan\pars{\theta \over 2} \equiv t}$:
\begin{align}&\color{#c00000}{\int_{0}^{1}%
\ln\pars{1 + x \over 1 - x}\,{\dd x \over x\root{1 - x^{2}}}}
=-4\int_{0}^{1}{\ln\pars{t} \over 1 - t^{2}}\,\dd t
=-4\int_{0}^{1}{\ln\pars{t^{1/2}} \over 1 - t}\,\half\,t^{-1/2}\,\dd t
\\[3mm]&=-\int_{0}^{1}{t^{-1/2}\ln\pars{t} \over 1 - t}\,\dd t
=\lim_{\mu \to -1/2}\partiald{}{\mu}\int_{0}^{1}{1 - t^{\mu} \over 1 - t}\,\dd t
\end{align}
Con la identidad
${\bf\mbox{6.3.22}}$ ( $\ds{\Psi\pars{z}}$ es la Función Digamma ${\bf\mbox{6.3.1}}$ y
$\ds{\gamma}$ es el de Euler-Mascheroni Constante ${\bf\mbox{6.1.3}}$ )
$$
\int_{0}^{1}{1 - t^{z - 1} \over 1 - t}\,\dd t
=\Psi\pars{z} + \gamma\etiqueta{$\bf 6.3.22$}
$$
\begin{align}&\color{#44f}{\large\int_{0}^{1}%
\ln\pars{1 + x \over 1 - x}\,{\dd x \over x\root{1 - x^{2}}}}
=\lim_{\mu \to -1/2}\partiald{\Psi\pars{\mu + 1}}{\mu} = \Psi'\pars{\half}
=3\ \underbrace{\zeta\pars{2}}_{\ds{{\pi^{2} \over 6}}}=
\color{#44f}{\Large{\pi^{2} \over 2}}
\end{align}
Ver ${\bf\mbox{6.4.4}}$.