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Differentiability question

  1. Apr 18, 2010 #1
    I want to show x->abs(x) is not differentiable at 0

    Some techniques in analysis are required.... how should i do?
     
  2. jcsd
  3. Apr 18, 2010 #2

    Landau

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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.
     
  4. Apr 19, 2010 #3
    More basically ... use the definition of derivative.
     
  5. Apr 19, 2010 #4

    Landau

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    The definition is the limit of the difference quotient.
     
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