Given

$\displaystyle

\int{\frac{cosh(x)}{3 sinh(x)+4}}

$

I come up with

$\displaystyle let u=sinh(x), du=cosh(x)$

$\displaystyle \int{\frac{du}{3u+4}}$

So

$\displaystyle \frac{1}{3}\int{\frac{du}{u}}+4$

And

$\displaystyle \frac{1}{3} sinh(x)+4x+C$

So, how many rules did I violate or otherwise offend with this one?