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Homework Help: Surface Integral

  1. Feb 24, 2010 #1

    bon

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    1. The problem statement, all variables and given/known data

    So trying to find the Integral of A.n dS where A is (y,2x,-z) and S is the surface of the plane 2x+y = 6 in the first octant cut off by the plane z=4

    2. Relevant equations



    3. The attempt at a solution

    So i always solve these by projection...but im a bit confused this time..

    normally the surface is in the form z=f(x,y) so i do z-f(x,y) and take grad to find the normal..

    so is the normal vector here just (2,1)? ie. grad 2x-y-6 = 0?

    In which case is the integral just the double integral of (y,2x,-4).(2,1,0) dA?

    Im a bit confused..Any help would be great!
     
  2. jcsd
  3. Feb 25, 2010 #2

    bon

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    Any ideas..?
    I'm pretty confused about which plane you project onto to solve this...

    Thanks!
     
  4. Feb 25, 2010 #3

    bon

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    So do you project onto y-z plane?

    and is the integral therefore the 1/2 times the double integral of A.(2,1,0) dydz?
     
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