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Math Help - coordinate geometry circle

  1. #1
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    coordinate geometry circle

    use coordinate geometry to show that a circle, with its centre at O(2,1) can be drawn through the points A(5,5) B(6,-2) and C (-2,2)
    what is the area of the circle?

    do i need to draw or can i calculate?
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  2. #2
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    Quote Originally Posted by decoy808 View Post
    use coordinate geometry to show that a circle, with its centre at O(2,1) can be drawn through the points A(5,5) B(6,-2) and C (-2,2)
    what is the area of the circle?

    do i need to draw or can i calculate?
    Calculate!
    Calculate the distance from the center of the circle to each of the points A,B,C.
    IF they are the same then you have a common distance, which is the radius.


    (Check your coordinates for point C.)
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  3. #3
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    Hello, decoy808!

    I believe there is a typo . . .


    Use coordinate geometry to show that a circle, with its centre at O(2,1)
    can be drawn through the points A(5,5), B(6,-2), and C(-2,-2)
    What is the area of the circle?
    Use the Distance Formula to show that: . OA \:=\:OB\:=\:OC
    . . That is, the center is equidistant from the three points.

    That distance is the radius of the circle.
    . . Now you can find the area of the circle, right?

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  4. #4
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    yes there was a type error at c. should be(-2,-2)

    i found the distances

    pa=5
    pb=7
    pc=7

    a=pi(r^2)
    =3.14 x 7^2
    =154

    is this correct. many thanks
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  5. #5
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    coordinate geometry circle

    posted by decoy808

    It is much easier to plot the points on coordinate paper.You see that B and C are points on different radii.You erect the slope diagram for the corrected C and find a 3,4 5 right triangle so the radius is 5


    bjh
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