I have a question where the students provide the lower, upper limits of integration, the integrand and the value.

The integral is measuring the area of a polar region. Thus, the limits of integration could be on any 2pi interval, but the lower limit = upper limit - pi.

I calculated

$upper = Compute("pi/2")->with(period => 2*pi);

As long as the student enters a correct possible upper limit, I want to check the lower limit as pi less than their upper limit. So I want

ANS($upper->cmp);

$lower = Compute("$studentsupper - pi");

ANS($lower->cmp);

I have been wanting to do something like this for a long time, but I've looked around and I'm not sure how to capture the student's answer to a question. Is there a system variable I can tap into? Do I need to use a postfilter? I've tried several things, but haven't come across anything that works.

Thanks, as always.

MEW