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Very basic partial derivatives problem

  1. Dec 29, 2009 #1
    Hello,
    I should feel ashamed to ask this, but it's giving me (and others) some troubles.

    given [tex]f(x_1,\ldots,x_n)[/tex], is it wrong to say that:

    [tex]\frac{\partial f}{\partial f}=1[/tex]

    ...?
     
  2. jcsd
  3. Dec 29, 2009 #2

    CompuChip

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    It doesn't make a lot of sense... the idea is that in the expression [itex]\frac{\partial f}{\partial x}[/itex], f is a function and x is a variable on which f does (or does not, or does indirectly) depend.

    You can write
    [tex]\frac{\delta f(x_1, \cdots, x_n)}{\delta f(x_1', \cdots, x_n')} = \delta(x_1 - x_1') \cdots \delta(x_n - x_n')[/tex]
    where the delta's on the right hand side are Dirac delta distributions, but you are taking functional derivatives then.
     
  4. Dec 29, 2009 #3
    uhm...it makes some sense in the following context:
    https://www.physicsforums.com/showthread.php?t=365940
    however, there must be a mistake but I cannot see it.

    [EDIT]: in the thread mentioned above a solution to the problem is described in its correct context. Sorry for this kind of "double posting"; in the beginning I thought I was facing a different problem than the original.
     
    Last edited: Dec 30, 2009
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