Arc Length for Hyperbolic Sin

[JCMateri]

I am having trouble with the arc length for hyperbolic sine. Can anyone help?

$$L=\int_{0}^{X}\sqrt{1+[\frac{dsinh(x)}{dx}]^2}dx=\int_{0}^{X}\sqrt{1+cosh^2(x)}dx$$

I'm having trouble evaluating the final integral.

 

[Mark44]

Wolfram Alpha reports that $\int \sqrt{1 + \cosh^2(x)}dx = \sqrt{\cosh^2(x)}\tanh(x) + C$

I suspect that it might be using a (hyperbolic) trig substitution to arrive at that result.