Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can anyone help me proofing this? This is not homework.

  1. Sep 23, 2010 #1
    This is part of a bigger derivation of Green's function. The book just jump to the ending and I cannot understand how to do this. I need someone to give me guidence how to proof this:

    [tex] \frac{x}{r} \frac{\partial u}{\partial x} + \frac{y}{r} \frac{\partial u}{\partial y} +\frac{z}{r} \frac{\partial u}{\partial z} \;=\; \frac{\partial u}{\partial r} [/tex]

    Where

    [tex] r=\sqrt{x^2+y^2+z^2}[/tex]

    This is not a homework problem.

    Thanks
     
  2. jcsd
  3. Sep 23, 2010 #2

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    Use the chain rule:

    [tex]\frac{\partial u}{\partial r}=\frac{\partial u}{\partial x}\frac{\partial x}{\partial r}+\cdots[/tex]
     
  4. Sep 23, 2010 #3
    I thought of that, but what is [tex]\frac{\partial x}{\partial r}[/tex]

    I know

    [tex]\frac{\partial r}{\partial x}=\frac{x}{r}[/tex]

    That's exactly where I got stuck!!!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Can anyone help me proofing this? This is not homework.
  1. Anyone can help me (Replies: 5)

Loading...