Chain rule for second derivatives

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Homework Help Overview

The discussion revolves around the application of the chain rule in the context of second derivatives in calculus. The original poster expresses confusion regarding the formulation of the chain rule for second derivatives, seeking clarification and resources for better understanding.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the validity of the original poster's expression for the second derivative and question the necessity of a distinct chain rule for second derivatives. There are attempts to clarify the application of the product rule and the role of mixed partial derivatives in the context of the problem.

Discussion Status

The discussion is ongoing, with participants providing feedback on the original poster's attempts and questioning the assumptions behind the formulation. Some guidance has been offered regarding the application of the chain rule and product rule, but no consensus has been reached on the correctness of the expressions presented.

Contextual Notes

There is an indication of uncertainty regarding the definitions and applications of derivatives, particularly in the context of changing variables. The original poster's request for external resources suggests a potential gap in foundational understanding.

ehrenfest
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Homework Statement


I cannot believe I do not know this!

[tex]dx/dt = dx/dt' dt'/dt[/tex] is the chain rule for first derivatives

[tex]d^2x/dt^2 = ?[/tex] is the chain rule for second derivatives

if it is complicated could you link me to a source that explains it please

Homework Equations


The Attempt at a Solution

 
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What's the problem with differentiating the first derivative?
 
[tex]d^2x/dt^2 = d^2x/(dt'dt) dt'/dt + dx/dt d^2t'/dt^2[/tex]?

The product rule was used. That mixed partial seems out of place. Is the above correct?
 
What makes you think there is a "chain rule for second derivatives"?
 
HallsofIvy said:
What makes you think there is a "chain rule for second derivatives"?

Well, is there something wrong with what I posted? Maybe I just discovered it.
 
ehrenfest said:
[tex]d^2x/dt^2 = d^2x/(dt'dt) dt'/dt + dx/dt d^2t'/dt^2[/tex]?

The product rule was used. That mixed partial seems out of place. Is the above correct?
Looks right. If you don't want the mixed partial, then why not apply the chain rule? After all, dx/dt' is merely a function... (Call it y, if you're having trouble thinking about it)
 

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