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Math Help - Equation of Circle

  1. #1
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    Equation of Circle

    I need help figuring out an equation. The equation of a circle with the center of the circle at the origin (0,0) on the Cartesian grid is: x^2+y^2=r^2.
    But what is the equation of the center of the circle is not at the origin?
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  2. #2
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    Quote Originally Posted by sunnyyueliang View Post
    I need help figuring out an equation. The equation of a circle with the center of the circle at the origin (0,0) on the Cartesian grid is: x^2+y^2=r^2.
    But what is the equation of the center of the circle is not at the origin?
    For a circle with centre (a,b) the equation is

    (x-a)^2 + (y-b)^2 = r^2
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  3. #3
    Senior Member pacman's Avatar
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    with center @ (h,k), it is (x - h)^2 + (y - k)^2 = (r)^2

    examples:

    i) (x - 2)^2 + (y - 3)^2 = 25

    ii) (x + 2)^2 + (y + 3)^2 = 9

    see graphs
    Attached Thumbnails Attached Thumbnails Equation of Circle-c1.gif   Equation of Circle-c2.gif  
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