Originally Posted by

**Vamz** Thanks!

I have a similar problem, I am trying to solve the way you suggested:

$\displaystyle

\displaystyle\int \frac{e^{6 x}}{e^{12 x} + 9} dx

$

let U=e^6x

$\displaystyle

\displaystyle\int \frac{U}{U^2+9}

$

now, if I pull a 1/9 out of the integral

I can get

$\displaystyle

\displaystyle\frac{1}{9} \int\frac{U}{\frac{U^2}{9}+1}

$

Aghh, and there is ALMOST an arctan there, if it wasnt for that U in the numerator!

What do I do here? Am I not supposed to use this same method?