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Help with an integral

  1. Nov 27, 2008 #1
    Hi there!
    I have to calculate the integral of the function sqrt(x^2+y^2) over the circle (x-1)^2+y^2<=1

    I use polar coordinates: rho goes from 0 to 2cos(theta) and theta goes from 0 to 2pi.
    My result is that the integral is 0... is it right?
  2. jcsd
  3. Nov 27, 2008 #2
    Yea I did it and got 0 because you end up integrating [itex]\cos(\theta)^3[/itex] at the end, which is 0.
  4. Nov 27, 2008 #3
    eohgan, if you think about what the geometric meaning of the integral is, it should be clear as to why your answer is zero.
  5. Nov 27, 2008 #4


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    Hi eoghan! :smile:

    erm … doesn't theta go from -π/2 to π/2? :redface:
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