Multivariable Calculus: Chain Rule and Second Derivatives

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SUMMARY

The discussion centers on the application of Clairaut's theorem in the context of multivariable calculus, specifically regarding the combination of partial derivatives dxdy and dydx. Participants clarify that Clairaut's theorem, which states that mixed partial derivatives are equal under certain conditions, is applicable here despite the confusion surrounding the second derivative. The distinction between 4s² and 4r² is also highlighted, emphasizing the importance of continuity of partial derivatives in this context.

PREREQUISITES
  • Understanding of multivariable calculus concepts
  • Familiarity with Clairaut's theorem
  • Knowledge of partial derivatives
  • Ability to interpret second derivatives
NEXT STEPS
  • Study the proofs and applications of Clairaut's theorem in multivariable calculus
  • Explore examples of continuity of partial derivatives
  • Learn about the implications of mixed partial derivatives in calculus
  • Review second derivative tests for functions of multiple variables
USEFUL FOR

Students of multivariable calculus, educators teaching calculus concepts, and anyone seeking to deepen their understanding of partial derivatives and their applications.

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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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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.
 

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