Higher Order Partial Derivatives and Clairaut's Theorem

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SUMMARY

Clairaut's Theorem asserts that for functions with continuous second partial derivatives, the mixed partial derivatives are equal, specifically fxy = fyx. This theorem extends to higher order partial derivatives, confirming that fxyz = fxzy = fzyx holds true under the same conditions. The discussion emphasizes the application of Clairaut's Theorem to third-order derivatives, providing clarity on the equality of mixed derivatives.

PREREQUISITES
  • Understanding of partial derivatives and their notation
  • Familiarity with Clairaut's Theorem
  • Knowledge of higher order derivatives
  • Basic calculus concepts
NEXT STEPS
  • Study the proof of Clairaut's Theorem in detail
  • Explore examples of higher order partial derivatives in multivariable calculus
  • Learn about the continuity conditions required for Clairaut's Theorem
  • Investigate applications of mixed partial derivatives in differential equations
USEFUL FOR

Students of multivariable calculus, mathematicians focusing on differential equations, and educators teaching advanced calculus concepts.

ChiralWaltz
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Homework Statement


general course question


Homework Equations


N/A


The Attempt at a Solution


fx is a first order partial derivative
fxy is a second order partial derivative
fxyz is a third order partial derivative

I understand that Clairaut's Theorem applies to second order derivatives, does it also apply to higher partial derivatives though?

Example:
fxy=fyx (Clairaut's)

So does this apply?
fxyz=fxzy=fzyx
 
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Yes it applies.
(1) fxy=fyx (Clairaut's)
We know that:
fxyz=(fx)yz
How can you prove that:
fxyz=fxzy using that?
 
Last edited:
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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