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Question about integrating

  1. Jul 14, 2014 #1

    When we have [tex]\frac{\partial}{\partial r}(r\frac{\partial p}{\partial r})=0[/tex]

    and we get

    [tex]r\frac{\partial p}{\partial r}=c_1[/tex]

    To get there, did we do this

    [tex]\int\frac{\partial}{\partial r}(r\frac{\partial p}{\partial r}) dr=\int 0 dr[/tex]


    [tex]\partial (r\frac{\partial p}{\partial r})=0\partial r[/tex]
    [tex]\int \partial (r\frac{\partial p}{\partial r})=\int 0\partial r[/tex]

    and why?

    Thanks in advance
  2. jcsd
  3. Jul 14, 2014 #2


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    Homework Helper

    Well, yes, but you could also think of it this way: This
    \frac{\partial}{\partial r} \left(r \frac{\partial p}{\partial r} \right) = 0

    tells you that the derivative wrt [tex] r [/tex] of the expression inside parentheses is zero, so that expression must be a constant.
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