Here is the problem is my textbook:
Suppose $s(x)$ is the arc length function for the curve $y=\sin x$ taking $(0,1)$ as the starting point. Find $sā(x)$.
According to arc length formula, I have :
$ L = \int_0^1 \sqrt{1+\left((\sin x)'\right)^2}dx = \int_0^1 \sqrt{1+\cos^2x}dx$
But this integral is hard to solve (and When I calculate in Maple, I cannot have the exactly result.) So, I cannot find $s(x)$ to calculate $sā(x)$
Thanks :)