Differentiating a constraint equation

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SUMMARY

The discussion focuses on finding the second derivative of the equation z = cr², where c is a constant. The first derivative is correctly identified as z' = 2crr'. The participant questions whether the second derivative can be expressed as z'' = 2cr'^2, but is advised to apply the product rule for differentiation, which indicates that r' should not be treated as a constant. The correct application of the product rule will yield the accurate second derivative, incorporating both r' and r'' terms.

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  • Familiarity with the product rule of derivatives
  • Knowledge of first and second derivatives
  • Basic algebra involving constants and variables
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Homework Statement



z = cr^2

Homework Equations





The Attempt at a Solution



I have a pretty simple question. What is the second derivative of the z equation.

I know that z' = 2crr'.

Am I correct to say that z'' = 2cr'^2 or is it something else?

Hopefully my question makes sense.
 
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There's a 2nd term involving r''. Use the product rule (fg)' = f' g + f g'.
 
Okay, thank you. That is what I was looking for. I just wasn't sure if I had to treat my r' as another variable or if I could consider it to be constant with the 2c. Thanks very much.
 

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