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Math Help - help determining angle

  1. #1
    ave
    ave is offline
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    help determining angle

    iv used the following formula to work out an angle between 2 points in 3d space

    cos t =((x1 * x2)+(y1*y2)+(z1*z2) )/ sqrt((x1*x1)+(y1*y1)+(z1*z1)) * sqrt((x2*x2)+(y2*y2)+(z2*z2))

    which works fine, I now need to know if the angle returned is a positive angle or negative one
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  2. #2
    MHF Contributor

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    Quote Originally Posted by ave View Post
    iv used the following formula to work out an angle between 2 points in 3d space

    cos t =((x1 * x2)+(y1*y2)+(z1*z2) )/ sqrt((x1*x1)+(y1*y1)+(z1*z1)) * sqrt((x2*x2)+(y2*y2)+(z2*z2))

    which works fine, I now need to know if the angle returned is a positive angle or negative one
    The angle is positive. If cos t itself is negative, that means t is between pi/2 and pi radians.
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