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Math Help - Vectors!! Trouble

  1. #1
    Member grgrsanjay's Avatar
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    Vectors!! Trouble

    Find the value of c such that,for all real x, the vectors cxI -6J +3K and xI +2J +2cxK make an obtuse angle with each other

    I means unit vector along x-axis!!
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  2. #2
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    Re: Vectors!! Trouble

    Hi
    Have you tried the dot product ?
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    Re: Vectors!! Trouble

    Quote Originally Posted by grgrsanjay View Post
    Find the value of c such that,for all real x, the vectors cxI -6J +3K and xI +2J +2cxK make an obtuse angle with each other
    First: please review this post. Have you written it correctly?

    Second: Two vectors form an obtuse angle if and only if their dot product is negative.
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  4. #4
    Member grgrsanjay's Avatar
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    Re: Vectors!! Trouble

    The vectors can form obtuse angle when Dot product is less than Zero...Thats it??
    Or is there any other condition??

    I get cx^2 - 12 + 6cx < 0,

    Then how should i proceed...c value must satisfy for all real x

    Thanks in Advance



    Sorry for the above thing!!!
    i got my answer woo hoo

    -4/3 < C < 0 Please verify my Answer
    Last edited by grgrsanjay; August 1st 2011 at 08:26 AM. Reason: I got my answer after posting this post...Sorry
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  5. #5
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    Re: Vectors!! Trouble

    I agree with your answer
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