Possible Duplicate:
Evaluating this integral for different values of a constant
Is there a solution to the definite integral, $\int\limits_{0}^{\infty} \frac{1}{x^{\frac{1}{n}}}\frac{1}{1+x^2}\mathrm{d}x$ where, $n \in \mathbb{N}$
HINT : substitute, $x = \tan\theta$