## difficult integration: int [ 1 / (1 + x^4) ] dx

integrate:

dx/ (1 + x[sup:2fussihg]4[/sup:2fussihg])

I've tried by parts using u = 1 / (1 + x[sup:2fussihg]4[/sup:2fussihg]) and dv = dx, but that only increased the power of the function

I also tried using the substitution x = SQRT(tant), with dx = sec[sup:2fussihg]2[/sup:2fussihg](t) / (2SQRT(tant)). This seemed to simplify it a bit but I still got stuck integrating.