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Quick calculus help

  1. Feb 27, 2009 #1
    1. The problem statement, all variables and given/known data

    [tex]\nabla[/tex] of (r^-2)rhat x zhat

    2. Relevant equations

    [tex]\nabla[/tex](AxB) = B([tex]\nabla[/tex]xA) - A([tex]\nabla[/tex]xB)


    Using cylindrical coordinates and curl in cylindrical with the above equation, I get zero?
    But I think I am wrong?
    Any help?
     
  2. jcsd
  3. Feb 28, 2009 #2

    Tom Mattson

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    I didn't get zero. Let's see what you did, then we can tell you where you're going wrong.
     
  4. Mar 1, 2009 #3
    I am using the formula for curl in spherical, I konw I said cylindrical.
    Taking the first cross product, zhat([tex]\nabla[/tex] x r^2 rhat) I use the ffact its in the rhat direction, so in the curl formula, sub r^2 for all r direction components. However they are then partially differentiated and I get zero, as the r^2 has no phi or theta components does it?
     
  5. Mar 1, 2009 #4

    Tom Mattson

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    You should be using cylindrical. "z" isn't a spherical coordinate.
     
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