Question

What is the derivative of `[pi(r)^2(h)]/3`?

Answer 1

It depends upon which variable you are basing your derivative on.
(see below)

Explanation:

Assuming `r` and `h` are independent variables:

`(d (pi(r)^2(h))/3)/(dr) = 2/3 pirh`

and

`(d (pi(r)^2(h))/3)/(dh) = (pir^2)/3`