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Math Help - Distance across a circle

  1. #1
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    Distance across a circle

    Hi there, I'm writing a computer program and I'm having a problem with the geometry. I would be very grateful for any help.
    My problem is that i have one fixed point on a circles perimeter and one point which is moving around the perimeter. Do you know how i can calculate the distance between the points at any time? I should add that i know the radius and the angle at which the moving point is in relation to the fixed. Does such a formula exist?
    Anyway, thanks for your time and any help would be amazing!
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  2. #2
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    If d is the distance between two points on a circle of radius a, and the angle subtended by the two radii to the two points is given by \theta, then we can use the Law of Cosines to compute the distance:

    d^{2}=a^{2}+a^{2}-2(a)(a)\cos(\theta).

    Can you simplify?
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  3. #3
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    Quote Originally Posted by Ackbeet View Post
    If d is the distance between two points on a circle of radius a, and the angle subtended by the two radii to the two points is given by \theta, then we can use the Law of Cosines to compute the distance:

    d^{2}=a^{2}+a^{2}-2(a)(a)\cos(\theta).

    Can you simplify?
    Thank you very much this is just what i'm looking for. I couldn't find the right expression anywhere. Thanks for your time and help!!
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  4. #4
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    You're welcome. Have a good one!
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