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Components using partial derivatives

  1. Jun 17, 2009 #1
    here is the question:
    http://i44.tinypic.com/xe53tc.gif

    here is the solution:
    http://i43.tinypic.com/2nuokfq.gif
    my first question regarding this whole thing is.
    why when the doing the partial derivative by "r" we dont multiply by minus
    the formula says (minus derivative)
    but all they do is making a derivative without multiplying by minus?
     
    Last edited: Jun 17, 2009
  2. jcsd
  3. Jun 17, 2009 #2

    tiny-tim

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    Hi transgalactic! :smile:
    erm :redface: … they're the same :confused:

    get some sleep! :zzz:​
    ?? :confused: but they have multiplied by the minus …

    ∂/∂r (1/r2) = -2/r3, and ∂/∂θ (cosθ) = -sinθ :smile:
     
  4. Jun 17, 2009 #3
    but we are doing a derivative by 'r'(partial derivative)
    we dont touch [tex]\theta [/tex] ,its constant
     
    Last edited: Jun 17, 2009
  5. Jun 17, 2009 #4
    i changed the original post
    now its ok
     
  6. Jun 17, 2009 #5

    tiny-tim

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    ok, but still ∂/∂r (1/r2) = -2/r3 :smile:
     
  7. Jun 17, 2009 #6
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