Hello,

Notice that the derivative of sinh(x) is precisely cosh(x)

In this case, substitution is the best way.

Substitute t=sinh(x) : it will eliminate cosh(x)

Then, you're left with the integral of arctan(t)

which can be done with an integration by parts, or again an substitution : t=tan(u)

Don't forget to substitute back once you're finished !