Calculus
# Arc Length and Surface Area

If ${f}'(x) = \sqrt{ {x}^4-1 },$ what is the length of the curve $y = f(x)$ from $x = 2$ to $x = 8?$

What is the length of the curve $y = \frac{1}{2}( {e}^x+{e}^{-x} )$ from $x = -13$ to $x = 13$?