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Math Help - Help me find a fitting equation

  1. #1
    Myx
    Myx is offline
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    Help me find a fitting equation

    Hello there!

    I'll just cut straight to the problem.
    I need a function f(X, Y) which takes two inputs ranging from -1 to 1.
    X and Y describes a circle.
    The function should give the following results:

    f( 0.0, -1.0) = 0
    f( 0.5, -0.5) = 0.25
    f( 1.0, 0.0) = 0.5
    f( 0.5, 0.5) = 0.75
    f( 0.0, 1.0) = 1
    f(-0.5, 0.5) = 1.25
    f(-1.0, 0.0) = 1.5
    f(-0.5, -0.5) = 1.75

    Any and all help is appreciated.
    (I apologize if I've posted in the wrong forum)

    // Myx
    Last edited by Myx; January 5th 2010 at 07:45 AM.
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  2. #2
    Super Member
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    Quote Originally Posted by Myx View Post
    Hello there!

    I'll just cut straight to the problem.
    I need a function f(X, Y) which takes two inputs ranging from -1 to 1.
    X and Y describes a circle.
    The function should give the following results:

    f( 0.0, -1.0) = 0
    f( 0.5, -0.5) = 0.25
    f( 1.0, 0.0) = 0.5
    f( 0.5, 0.5) = 0.75
    f( 0.0, 1.0) = 1
    f(-0.5, 0.5) = 1.25
    f(-1.0, 0.0) = 1.5
    f(-0.5, -0.5) = 1.75

    Any and all help is appreciated.
    (I apologize if I've posted in the wrong forum)

    // Myx
    I've made a sketch from the given points. It seems to me that these points belong to a helix:

    \left|\begin{array}{l}x=\cos\left(t-\frac \pi2\right) \\ y=\sin\left(t-\frac \pi2\right) \\ z=\frac1\pi t\end{array}\right.

    EDIT: I've attached the sketch. As you can see there are some points which doesn't fit into the parametric equation I gave you. So you have to modify probably the equation a little bit
    Attached Thumbnails Attached Thumbnails Help me find a fitting equation-helix_pktmenge.png  
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  3. #3
    Myx
    Myx is offline
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    Ah, that did the trick. Thank you!
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