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Math Help - Equation of a circle

  1. #1
    Senior Member euclid2's Avatar
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    Equation of a circle

    A(4,3) and B(-4,-3) are the endpoints of the diameter of a circle. Determin the center of the circle and the equation of the circle.
    I found the center as (0,0) by using the midpoint formula.
    where do i go from here?
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  2. #2
    o_O
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    Recall the equation of a circle: (x - h)^{2} + (x - k)^{2} = r^{2}

    where (h,k) is the coordinate of circle's centre and r (not r^2) is your radius.

    You have your centre and you can easily find the radius via the pythagorean theorem (draw a line to the coordinate (4,3) and a right-angled triangle can be constructed) or the distance formula. Whichever.
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