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Homework Help: Equation of a circle / polar coordinates

  1. Dec 4, 2011 #1
    I was looking at the equation of a circle in polar coordinates on wikipedia,

    http://en.wikipedia.org/wiki/Polar_coordinate_system

    and I understand that a is the radius of the circle, and that (r0, phi) is the center of the circle. But I don't see what the r and theta refer to :(.
     
  2. jcsd
  3. Dec 4, 2011 #2

    eumyang

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    r and θ are just the variables in the equation.

    Just like in rectangular coordinates, given a center (h, k) and radius r,
    (x - h)2 + (y - k)2 = r2
    is the equation of the circle, and x and y are the variables.

    Or am I misunderstanding your question? :confused:
     
  4. Dec 4, 2011 #3
    So do they just represent a point inside the circle?
     
  5. Dec 4, 2011 #4

    eumyang

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    No, they represent a set of points that lie on the circle, not inside.
     
  6. Dec 4, 2011 #5
    What do you mean by [[/B]on[/B]? And by the way; sorry for giving you a hard time. English is not my first language.
     
  7. Dec 4, 2011 #6

    eumyang

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    See attached picture. The red point is on the circle, while the blue point is inside the circle.
     

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