Tuesday 25 December 2012

real analysis - Need help to evaluate $I_n=int_{0}^{infty}e^{-x}sin(nln(x))dx$

For $n\in\mathbb{N}$, I'm trying to find a closed form for the following integrals :
$$I_n=\int_{0}^{\infty}e^{-x}\sin(n\ln(x))\text{d}x$$



My real objective is to evaluate $\sum\limits_{n=1}^{\infty}\frac{I_n}{n}$, and since interchanging the sum and the integral didn't lead anywhere, I suppose that finding a closed form expression for $I_n$ is the way to go, but I'm lost as of how to proceed...



Maybe the residue theorem/contour integration could help, but I'm not familiar with complex analysis so I haven't tried it - feel free to use it though.



Any suggestion ?

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