The Gateway Arch to the West in St. Louis has the shape of an inverted catenary. Rising 630 ft at its center and stertching 630 ft across its base, the shape of the arch can be approximated by

$\displaystyle y=-127.7 cosh\left(\frac{x}{127.7}\right) + 757.7$ for $\displaystyle -315\le x \le 315$

Approximate the total length of the arch.

Is this a problem involving derivatives of integrals because I'm kind of lost at this word problem. I'm thinking take the derivative with respect to x.