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Domain Differentiation question

  1. Dec 10, 2012 #1
    if a function f is differentiable of [0,2pi] can I integrate its derivative df on [-pi, pi]?
  2. jcsd
  3. Dec 10, 2012 #2
    First of all, df is not the derivative of f, it is the differential of f, ##\frac{df}{dx}## is the derivative of x (assuming f is a function of x).

    Second of all, why would you think that it's derivative would have a different domain?
  4. Dec 11, 2012 #3


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    The function, f(x)= 0 if x< 0 and rational or [itex]x> 2\pi[/itex] and rational, f(x)= 1 if x< 0 and irrational or [itex]x> 2\pi[/itex] and irrational, f(x)= 3 for all other x, is differentiable for all x in [itex][0, 2\pi][/itex] but not differentiable for any other f. Since it does not have a derivative on [itex][-\pi, 0][/itex], no, its derivative cannot be integegrated there!
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