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Homework Help: Partial derivative question

  1. Oct 17, 2007 #1
    I'm confused on a procedural idea...

    If I'm doing the cross product of a gradient and 'the x component of a force' , so:

    [tex] \nabla X F(x) = \frac{\partial}{\partial z} Fy [/tex]

    and Fy = x..

    even though im differentiating with respect to z , im solving for an x component, which means I can not take x out with the other constants.... yes? (if there were some)

    I guess I'm confused because I know this shouldn't = 0 afterwards, but I'm not differentiating wrt z, so I'm trying to figure out why.

    Thanks alot !

    (F(z) is 0 in case your wondering why its only Fy.)
  2. jcsd
  3. Oct 17, 2007 #2


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    Staff Emeritus
    Science Advisor

    Is one looking at something like this?

    [tex]det \[ \left[ \begin{array}{ccc}
    \hat{x} & \hat{y} & \hat{z} \\\
    \frac{\partial}{\partial{x}} & \frac{\partial}{\partial{y}} & \frac{\partial}{\partial{z}} \\\
    F_x & F_y & F_z \end{array} \right]\] [/tex]
  4. Oct 17, 2007 #3
    yes I am...
    thats how I set up the equation, but I don't know if I may take x out or not.
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