Want help solving $\int_0^1\frac{\ln(1+x)}{\ln(1-x)}dx$

calculusdefinite integralsintegration

When attempting to solve

$$\int_0^1\frac{\ln(1+x)}{\ln(1-x)}dx$$

I attempted using the Taylor series expansion of $\ln(1+x)$ first, but that came to no avail. I also tried splitting it up a bit with integration by parts by multiplying top and bottom by x, and then integrating $\frac{\ln(1+x)}{x}$ and differentiating $\frac{x}{\ln(1-x)}$, but I had no clue what to do with the functions involving $\mathrm{Li_2}(-x)$. I know the integral converges I'm just not sure how else to go about solving it.

Best Answer

You can get an exponentially convergent series in the following: \begin{align} \int_0^1 \frac{\log(1+x)}{\log(1-x)} \, {\rm d}x &= \int_0^1 \frac{\log(2-x)}{\log(x)} \, {\rm d}x \\ &=\log(2-x) {\rm li}(x) \Big|_0^1 + \int_0^1 \frac{{\rm li}(x)}{2-x} \, {\rm d}x \\ &=\frac{1}{2} \sum_{n=0}^\infty \frac{1}{2^n}\int_0^1 {\rm li}(x) x^n \, {\rm d}x \\ &=-\sum_{n=0}^\infty \frac{\log(2+n)}{(n+1)\,2^{n+1}} \, . \end{align}