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Homework Help: Vector integral question

  1. Sep 14, 2010 #1
    1. The problem statement, all variables and given/known data

    doubleintegral.jpg

    3. The attempt at a solution
    I get parts a and b, but I don't know what to do for part c.
    I can write a double integral with dx and dz (because y is constant) and substitute y=7 in, but I'm not sure how to integrate ax...

    Any hints would be appreciated.
     
  2. jcsd
  3. Sep 14, 2010 #2

    diazona

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    First, is ax constant over the integration region? If so, you can pull it out of the integral, just as with a numeric constant.

    If it's not constant, you'd need to find a way to express it in terms of things (i.e. other unit vectors) that are constant.
     
  4. Sep 14, 2010 #3
    Well I guess ax is a unit vector in the x direction, so it must be constant.

    But how do I figure out the limits of integration for x and z?
     
  5. Sep 14, 2010 #4

    diazona

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    Well, what's the region of integration?
     
  6. Sep 14, 2010 #5
    I don't know, it just says plane y=7.
     
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