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Homework Help: Mass of a surface

  1. Apr 11, 2009 #1
    1. The problem statement, all variables and given/known data
    If the mass per unit area of a surface is given by rho = x*y, find the mass
    double integral over S of x*y dS if S is the part of the cylinder x^2 + z^2 = 9 which is in the first octant and contained within the cylinder x^2 + y^2 = 4.

    2. Relevant equations

    3. The attempt at a solution
    I can visualize what the shape looks like, but I'm not sure how to define the bounds of integration based on the shape described.
  2. jcsd
  3. Apr 11, 2009 #2
    does anyone have any ideas? help would be greatly appreciated.
  4. Apr 13, 2009 #3
    Make sure you're visualizing the shape from a useful viewpoint. I suggest looking "from above." In other words, draw the xy-plane as usual on your paper, position your eye directly above the origin, and imagine the z-axis pointing straight out at your eye. Shade the region in the xy-plane that is covered by the surface.
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