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Homework Help: Double integrate help

  1. Mar 30, 2008 #1
    1. The problem statement, all variables and given/known data

    Using polar coordinates, evaluate the integral which gives the area which lies in the first quadrant below the line y=7,and between the circles x^2 + y^2 = 196 and x^2 - 14x + y^2 = 0.

    2. Relevant equations



    3. The attempt at a solution

    i tried to double integrate from 0<theta<pi/2, 7-14cos(theta)<r<7 with rdrd(theta) but that was not the correct answe, can someone tell me with i did wrong with the r values
     
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  3. Mar 31, 2008 #2

    Dick

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    Did you draw a picture of the region you are integrating? If I'm drawing it correctly it doesn't look like you can do it as a single integral. You'll need to break it into pieces and think about using different origins for the polar coordinates for different pieces. Looks kind of nasty.
     
  4. Mar 31, 2008 #3
    yes, i did, even ask my professor on how to doing it, but she only gave me the r=7+7cos(theta) but that doesn't make sense, i thought it's 14cos(theta), Dick, i completely loss, can anyone help me on this one
     
  5. Mar 31, 2008 #4

    Dick

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    First of all there are three curves to worry about. The circle of radius 14, the circle of radius 7 and the line y=7. Which one corresponds to the polar equation r=7+7cos(theta)? What are the polar equations of the other two?
     
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