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Homework Help: Partial Differentiation [Subscript]

  1. May 25, 2009 #1


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    What does the subscript outside a partial differentiation mean? For example:

    [tex]\left(\frac{\partial x}{\partial y}\right)_z[/tex]

    What does the [tex]z[/tex] mean above?
  2. jcsd
  3. May 25, 2009 #2


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    It means "holding z constant".
  4. Aug 10, 2011 #3
    Is that any different from a regular partial derivative though? I've started to encounter the notation in literature and am finding it strange.
  5. Aug 11, 2011 #4

    Ray Vickson

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    It is rarely used in Mathematics, but is used often in some fields such as Thermodynamics. Basically, it indicates that we are considering x to be a function of y and z, without using notation like x(y,z).

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