Is the Function x->|x| Differentiable at 0?

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    Differentiability
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Discussion Overview

The discussion centers around the differentiability of the function \( x \mapsto |x| \) at the point \( 0 \). Participants explore various techniques and definitions related to the concept of differentiability, particularly in the context of analysis.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant expresses a desire to demonstrate that \( x \mapsto |x| \) is not differentiable at \( 0 \) and seeks guidance on techniques in analysis.
  • Another participant suggests calculating the left and right limits of the difference quotient, noting that if the function were differentiable, these limits would need to coincide.
  • A more basic approach is proposed by a participant, who recommends using the definition of the derivative.
  • Another participant reiterates that the definition involves the limit of the difference quotient.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the differentiability of the function at \( 0 \), and multiple approaches are suggested without resolution.

losin
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I want to show x->abs(x) is not differentiable at 0

Some techniques in analysis are required... how should i do?
 
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Calculate left and right limit of the difference quotient. If the function were differentiable, these would coincide, but they don't.
 
More basically ... use the definition of derivative.
 
The definition is the limit of the difference quotient.
 

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