A cable hangs between two poles of equal height and $26$ feet apart. Set up a coordinate system where the poles are placed at $x = -13$ and $x = 13$, where $x$ is measured in feet. The height (in feet) of the cable at position $x$ is

$$h(x) = 8 \cosh(x/8),$$
where $\cosh(x) = (e^x + e^{-x})/2$ is the hyperbolic cosine, which is an important function in physics and engineering.
The cable is feet long.