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Green's theorem

  1. Sep 24, 2009 #1
    1.find the line integral of
    (x^3-y^3)dx +(x^3+y^3)dy over r, where r is the boundary of the
    region limited by x^2+y^2=1 and x^2+y^2=9

    2. Relevant equations

    i found that the
    line integral over the curve x^2+y^2=1 is 3*Pi/2
    and the double integral of the region limited by x^2+y^2=1 and x^2+y^2=9 is 120*Pi
    so the answer would be 120*Pi + 3*Pi/2 ???

  2. jcsd
  3. Sep 24, 2009 #2


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    Homework Helper

    The question is not very clear. The region between x^2+y^2=1 and x^2+y^2=9 consists of two curves that aren't connected. A proper question would specify the direction for each part of the contour. 120*pi is correct if you make a certain assumption about the direction of each contour. Whoever is giving you these questions should really work on phrasing them better.
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