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October 29th, 2012, 08:35 AM   #1
lo2
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Interpretating partial derivatives of a function of two vari

Hi there

I have this function, which is the function for determining the body mass index (BMI):



Then I have to determine these two values:





And then I have to interpret these values, and I guess C is how much B changes when you go along the m-axis (which in this case is the x-axis). But is there a like more tangible meaning to this value? It seems like it, but I am just not able to spot it :/
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October 29th, 2012, 12:51 PM   #2
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Re: Interpretating partial derivatives of a function of two

Quote:
Originally Posted by lo2
Hi there

I have this function, which is the function for determining the body mass index (BMI):



Then I have to determine these two values:





And then I have to interpret these values, and I guess C is how much B changes when you go along the m-axis (which in this case is the x-axis). But is there a like more tangible meaning to this value? It seems like it, but I am just not able to spot it :/
C is the rate at which B is changing if you change only m, D is the rate at B is changing if you change only h. More than that cannot be said without knowing what "m" and "h" mean.
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October 29th, 2012, 02:15 PM   #3
lo2
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Re: Interpretating partial derivatives of a function of two

m is weight in kilograms and h is height in meters.

So the change in m, does not depend on m itself, it rather depends on h?
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October 29th, 2012, 02:23 PM   #4
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Re: Interpretating partial derivatives of a function of two

Yes, that is correct: If we write then so that B is a linear function of m with slope so that if m changes by some amount, then B changes by time the change in m, not m itself.
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