I tried to evaluate the length of this curve but cannot figure out what to do with the derivative of the log(cost). The question is:

Find the length of the curve r(t) = <1, log(cost)>

t having the domain [0, pi/4]

I did the integral from 0 to pi/4 of the square root of the sum of the derivative of the components and im having trouble integrating it. Can anyone help me solve this?