# Thread: Area of cycloid using integration

1. ## Area of cycloid using integration

Look at the first 2 steps of integration. How come the upper limit in the second step is $2\pi$ instead of $2a\pi$?

2. ## Limits of integral

Hello chengbin
Originally Posted by chengbin

Look at the first 2 steps of integration. How come the upper limit in the second step is $2\pi$ instead of $2a\pi$?
Because the variable has been changed from $x$ to $\theta$ (note, we're now integrating with respect to $\theta$). And the limits are $\theta = 0$ to $2\pi$.