Multivariable Calculus: Chain Rule and Second Derivatives

In summary, the conversation discusses a problem and solution involving the combination of dxdy and dydx, using Clairaut's theorem. There is confusion around the second derivative and the equality of mixed partials. The solution involves continuity of partials and there is a theorem in the textbook that addresses this.
  • #1
theBEAST
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Homework Statement


Here is the problem with the solution:
http://dl.dropbox.com/u/64325990/MATH%20253/Capture.PNG

What I don't understand is circled in red, how did they combine dxdy with dydx? Is it with Clairaut's theorem? If it is can someone explain how it works in this case because the second derivative makes this very confusing. Additionally 4s^2 ≠ 4r^2 so how can you use Clairaut?
 
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  • #2
That's the "By continuity of partials". There's a theorem regarding continuity of partials and the equality of mixed partials. I'm sure it's in your text. You should check it out. It's kind of a big deal.

Yes it's Clairaut.
 

Related to Multivariable Calculus: Chain Rule and Second Derivatives

1. What is the chain rule in multivariable calculus?

The chain rule in multivariable calculus is a method for finding the derivative of a composite function. It states that the derivative of a composite function is equal to the derivative of the outer function multiplied by the derivative of the inner function.

2. Why is the chain rule important in multivariable calculus?

The chain rule is important in multivariable calculus because it allows us to find the rates of change of complex functions. This is crucial in many fields of science, such as physics, engineering, and economics.

3. How do you use the chain rule to find the derivative of a multivariable function?

To use the chain rule to find the derivative of a multivariable function, you need to identify the inner and outer functions. Then, take the derivative of the outer function and multiply it by the derivative of the inner function, which can be found using the partial derivative notation.

4. What is the second derivative in multivariable calculus?

The second derivative in multivariable calculus is the derivative of the first derivative. It measures the rate of change of the slope of a function, and it can tell us information about the curvature of a graph.

5. How do you find the second derivative of a multivariable function?

To find the second derivative of a multivariable function, you need to take the derivative of the first derivative using the partial derivative notation. This will result in a second derivative function, which can then be evaluated at a specific point to find the second derivative value at that point.

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