Hi, i am a little confused with this concept:
A cylinder has dimensions r=5, h=10. FInd the approximate increase in volume when r increases by 0.2 and h decreases by 0.1.
I can get the correct answer by using partial derivatives, but dont understand why you cant just put the new set of numbers into the formula for the volume of a cylinder and compare the answers?
Why do they give different results, and just pluggign the numbers in is wrong?
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Why Do We Need Partial Derivatives? watch
- Thread Starter
- 07-02-2010 14:07
- 07-02-2010 14:50
The point of using partial derivatives here is that it gives you a way of actually analysing how changes in the input affect the output. This is often important in understanding how a larger system behaves.
But for the actual example, yeah, it's easier to just plug the numbers in, and you get a more accurate result that way as well. (Just plugging in the numbers is only "wrong" in that it's not what the question asks you do to. It's a perfectly reasonable way of finding the change in practice).