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Math Help - Rotation matrix

  1. #1
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    Rotation matrix

    Hi Guys and Girls,

    I have the following problem and have no idea about where to start.

    Give an example of a 2 by 2 rotation matrix that rotates the point
    ( 7 , 7 )
    into the square with corners
    ( -1 , -10 )
    ( 1 , -10 )
    ( 1 , -8 )
    ( -1 , -8 )



    I have a feeling that I would need to use the rotation matrix

    Cos(x) -Sin(x)
    Sin(x) Cos(x)

    But am confused as to what the points would be.


    Thanks

    KJx



    n
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  2. #2
    MHF Contributor
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    Re: Rotation matrix

    Hey KingJohnno.

    Hint: Try expanding out your linear system to get solutions in terms of sin(x) and cos(x) and then find x with respect to the right quadrant using arc-cos and arc-sin.
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  3. #3
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    Re: Rotation matrix

    Here's a solution and a general rotation matrix for such problems:

    Rotation matrix-mhfrotationmatrixa.png
    Last edited by johng; February 20th 2013 at 09:45 PM.
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  4. #4
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    Re: Rotation matrix

    Brilliant - Thanks for your help John. (we share the same initials!) I sort of understand what is going on now, I emailed my tutor and he went through it with me! Thank you :-)
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