1. ## Hyperbolic functions

Hi i am trying to take the derivative of a hyperbolic function but i can not figure out what to use for my u subsitution, the function is:
sqrt(4x+cosh^2(5x))
$\displaystyle \frac{{\rm{d}}}{{{\rm{dx}}}}\left[ {\cosh ^n \left( {f(x)} \right)} \right] = n\cosh ^{n - 1} \left( {f(x)} \right)\sinh \left( {f(x)} \right)f'(x)$