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Non-differentiable function

  1. Sep 18, 2012 #1
    I know that [itex]e^{rx}[/itex] is an infinitely differentiable function.
    However, say you have f= x. this is clearly one time differentiable, giving 1. a second time it can be derived as well, giving 0. is 0 differentiable, indeed differentiation gives zero.
    So when is a function non-differentiable. i'm thinking of cusps, such as on x=0 with the function f=|x|, or other functions where the derivative is undefined. correct? are there other cases? it would also be interesting to see a function that is only finitely differentiable.
    Last edited: Sep 18, 2012
  2. jcsd
  3. Sep 18, 2012 #2


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  4. Sep 18, 2012 #3
    that's a nice one!
  5. Sep 18, 2012 #4


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  6. Sep 18, 2012 #5
    thanks, will apply that formula.
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