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Homework Help: Area of circle in polar coordinates

  1. Dec 13, 2014 #1
    1. The problem statement, all variables and given/known data
    r=2cos(theta) I want to find the area using polar integration.

    2. Relevant equations
    area=(1/2)r^2 from 0-pi

    3. The attempt at a solution
    When I plug everything in I get 2pi as the answer. I'm in multivariable calculus so this is very frustrating. What am I doing wrong, I don't know, but it's really really really really bugging me. I have an extra 2 somewhere and I don't know where.
  2. jcsd
  3. Dec 13, 2014 #2
    EDIT: I don't know how to delete a post but I got it. My calculator was in degree mode.
  4. Dec 13, 2014 #3


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    Gold Member

    While you may have gotten the correct answer, if you plot that circle you will see that the appropriate interval of integration would be ##[-\frac \pi 2,\frac \pi 2]##, not ##[0,\pi]##.
  5. Dec 13, 2014 #4
    It works both ways, does it not?
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