The total derivative and a line segment S

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SUMMARY

The discussion focuses on proving that for a differentiable function \( f \) defined on an open set \( U \subseteq \mathbb{R}^n \), the equation \( f(y) - f(x) = (Df)_{\xi}(y - x) \) holds for some \( \xi \in S \), where \( S = \{(1-t)x + yt : t \in [0,1]\} \). Participants emphasize the necessity of employing the chain rule and the mean value theorem to establish this relationship. The proof hinges on the properties of differentiable functions and the continuity of derivatives within the segment \( S \).

PREREQUISITES
  • Differentiable functions in multivariable calculus
  • Understanding of the mean value theorem
  • Application of the chain rule in calculus
  • Knowledge of open sets in \( \mathbb{R}^n \)
NEXT STEPS
  • Study the mean value theorem for functions of several variables
  • Review the chain rule for multivariable functions
  • Explore the properties of differentiable functions on open sets
  • Practice proving relationships involving derivatives and segments in \( \mathbb{R}^n \)
USEFUL FOR

Students and educators in advanced calculus, particularly those focusing on multivariable functions and their properties, as well as anyone preparing for exams involving differentiability and the application of the mean value theorem.

Demon117
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Homework Statement



Let f be a differentiable function from an open set

[tex]U\subseteqR^{n}[/tex] into R. If

[tex]x,y\inU[/tex] and the segment [tex]S={(1-t)x+yt : t\in[0,1]}[/tex] is contained in U, show that

[tex]f(y)-f(x)=(Df)_{\xi}(y-x)[/tex] for some [tex]\xi\inS[/tex].



The Attempt at a Solution


The only direction I have is that I need to use the chain rule and the mean value theorem. Beyond that I do not know how to proceed.
 
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matumich26 said:

Homework Statement



Let f be a differentiable function from an open set

[tex]U\subseteqR^{n}[/tex] into R. If

[tex]x,y\inU[/tex] and the segment [tex]S={(1-t)x+yt : t\in[0,1]}[/tex] is contained in U, show that

[tex]f(y)-f(x)=(Df)_{\xi}(y-x)[/tex] for some [tex]\xi\inS[/tex].



The Attempt at a Solution


The only direction I have is that I need to use the chain rule and the mean value theorem. Beyond that I do not know how to proceed.

Totally screwed up the latex code here. Sorry.
 

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