Need help finding maximum values over 3-d parameters?

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If you look into my work so far I was trying to solve under a specific section of a function using the left-endpoint rule, since it can't be computed explicitly.

In this case e is the change of the function by x, and f is the change by y. And z is equal to the area under an equation from $a=0$, to $b=2\pi$, where the area is positive. You can see here: https://www.desmos.com/calculator/kv4...

I tried to make a 3-d parameter by making $m(x)=e$, $m(y)=f$, and $m(z)=q$, and tried to find the maximum values of e, and f. I've tried using sage's programming, but there is something wrong with what I did as seen here: https://cloud.sagemath.com/projects/1...

Is there a way of finding the maximum value of e, and f values? If it is done correctly both of them should be calculated as $e=0$, and $f=0$, since this should have the maximum value of $q$.