Quote:
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Originally Posted by Kevin Sevcik
if you try deriving just the second equation, then h is a variable, and you end up with a dh/dr term that you need a value for. substituting from the volume equation gets rid of this term because V is a constant in this case.
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Yes, but I was taking the
partial derivative, so you just consider
h a constant to take the derivative (that's far from a formal mathematical statement, but I don't know the exact English terms to make it more appropriate
).
I agree that the height and the radius are constrained by the fixed volume, but I don't see how that changes my solution.
It seems Sanddrag is taking Calculus A, or I, or 101, or whatever you call it in the USA. I didn't learn about partial derivatives until Calculus II.