Some Integrals

[man111]

$\displaystyle (1)\;\; \int_{-\infty}^{\infty}\frac{x^2}{1+4x+3x^2-4x^3-2x^4+2x^5+x^6}dx$

$\displaystyle (2)\;\; \int_{0}^{\frac{\pi}{2}}e^{-\left(\pi.\tan x - 1\right)^2}dx$

$\displaystyle (3)\;\; \int \frac{1}{\sqrt{1-x^4}}dx$