Clairaut's Theorem: Continuous 1st Derivatives?

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SUMMARY

Clairaut's Theorem asserts that if the second derivatives of a function, specifically fxy and fyx, are equal, then the first derivatives, fx and fy, are continuous. This conclusion is based on the requirement that for second-order partial derivatives to exist, the first-order partial derivatives must be differentiable and continuous on the same set. Furthermore, if both second-order partial derivatives exist and are equal, they are also continuous on that set, establishing a reciprocal relationship.

PREREQUISITES
  • Understanding of partial derivatives
  • Familiarity with differentiability concepts
  • Knowledge of continuity in calculus
  • Basic grasp of Clairaut's Theorem
NEXT STEPS
  • Study the implications of Clairaut's Theorem in multivariable calculus
  • Explore examples of functions demonstrating continuous first derivatives
  • Investigate the relationship between differentiability and continuity
  • Learn about higher-order derivatives and their properties
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Mathematics students, educators, and professionals in fields requiring advanced calculus knowledge, particularly those studying multivariable functions and their properties.

alexio
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If second derivatives of function,f, fxy and fyx, are equal,
are the first dervitives, fx and fy, continuous?
 
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alexio said:
If second derivatives of function,f, fxy and fyx, are equal,
are the first dervitives, fx and fy, continuous?
Yes. For the second order partial derivatives of a function to exist on some set, the first order partial derivatives must be differentiable and hence continuous on that same set. More interestingly, if both second order partial derivatives exist are are equal on some set, then they are both continuous on that same set. The opposite statement is also true.
 

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