How to calculate $\int_{0}^{\pi/3} \sqrt{\sec ^2 (x)} dx$? I'm trying to calculate the following integral:
$\int_{0}^{\pi/3} \sqrt{\sec^2 (x)} dx$
But I have no idea where to start. Can you give me some advice?

Find the interval(s) where $\sec(x)$ is positive vs. negative in $[0,\pi/3].$ then you can get rid of the absolute values (inserting $-$ if negative) and integrate $\sec(x)$ instead.
