Find the arc length of the curve r(t)=(cost,sint,2t)\mathbf{r}(t) = (\cos t, \sin t, 2t)r(t)=(cost,sint,2t) from t=0t = 0t=0 to t=π2t = \frac{\pi}{2}t=2π.
π2\frac{\pi}{2}2π
π52\frac{\pi\sqrt{5}}{2}2π5
5\sqrt{5}5
π5\pi\sqrt{5}π5