Chain rule for second derivatives

In summary, the conversation discusses the chain rule for first and second derivatives and the use of the product rule and chain rule in differentiating these derivatives. The concept of a "chain rule for second derivatives" is questioned and the application of the chain rule is suggested as an alternative. Additional clarification and explanation is requested.
  • #1
ehrenfest
2,020
1

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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  • #2
What's the problem with differentiating the first derivative?
 
  • #3
[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?
 
  • #4
What makes you think there is a "chain rule for second derivatives"?
 
  • #5
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.
 
  • #6
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)
 

1. What is the chain rule for second derivatives?

The chain rule for second derivatives is a mathematical rule that allows us to find the second derivative of a composite function, where the input of the function is itself a function. It is used to find the rate of change of a rate of change.

2. Why is the chain rule for second derivatives important?

The chain rule for second derivatives is important because it allows us to analyze more complex functions and understand how changes in one variable affect the rate of change of another variable. It is essential in many fields of mathematics, physics, and engineering.

3. How is the chain rule for second derivatives applied?

The chain rule for second derivatives is applied by first finding the first derivative of the outer function, then finding the first derivative of the inner function, and finally multiplying these two derivatives together. The result is then differentiated again to find the second derivative.

4. What is an example of using the chain rule for second derivatives?

One example of using the chain rule for second derivatives is in the study of motion, where acceleration is the second derivative of position with respect to time. By using the chain rule, we can find the acceleration of a moving object with respect to a changing variable, such as velocity or time.

5. Are there any common mistakes when using the chain rule for second derivatives?

Yes, some common mistakes when using the chain rule for second derivatives include forgetting to differentiate the inner function, mixing up the order of differentiation, and not considering the product rule when multiplying the two derivatives. It is important to carefully follow the steps and double-check the calculations to avoid errors.

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