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Math Help - Need help with vectos

  1. #1
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    Need help with vectos

    Hi please help me with this! How do I do part b!

    I thought to find the midpoint of B and the negative y-axis, and then equate the y-coordinate to sqrt(14) but that did not seem to be the way..
    Attached Thumbnails Attached Thumbnails Need help with vectos-screen-shot-2013-02-02-pm-02.20.31.png  
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  2. #2
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    Re: Need help with vectos

    Hey Tutu.

    (Hint: Try using Pythagoras' Theorem).
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  3. #3
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    Re: Need help with vectos

    But how, I do not know the coordinates of the other end of B?
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  4. #4
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    Re: Need help with vectos

    You know the height of B and you know the hypotenuse.

    Use the fact that a^2 + b^2 + c^2 = d^2 where you know d = SQRT(14) and a = -1, b = 2. (I'm using a 3D version of the Pythagoras' Theorem).
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  5. #5
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    Re: Need help with vectos

    Sorry, how did you get a^2 + b^2 + c^2 = d^2 ? And how did you get those values..?
    Sorry
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  6. #6
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    Re: Need help with vectos

    This is the form of the distance formula in three dimensions (as opposed to the one in two).

    The hypotenuse is given in the question and the rest is found from the values in your diagram.
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  7. #7
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    Re: Need help with vectos

    I just went to search online,

    they said a is the left right distance, b is the front back distance and c is the up down distance.
    I understand why a^2 + b^2 + c^2 = d^2 but then shouldn't a be -1, b be -1, and c be 2?
    How did you know sqrt 14 is the distance? The more I look at the diagram, it looks like the midpoint!
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  8. #8
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    Re: Need help with vectos

    You are right in that a = -1 and b = -1 and you need to find a value of c where d = SQRT(14).
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  9. #9
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    Re: Need help with vectos

    I got c to be sqrt(12)?
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  10. #10
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    Re: Need help with vectos

    That looks right.
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  11. #11
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    Re: Need help with vectos

    But from there, how do I find the two coordinates on the y-axis?
    Sorry that I still cannot get this!
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  12. #12
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    Re: Need help with vectos

    Find the y-point +- SQRT(12) of the B's y-point (which is -1 according to the diagram).
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  13. #13
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    Re: Need help with vectos

    So it's -1+sqrt(12) and -1-sqrt(12)?
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  14. #14
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    Re: Need help with vectos

    Yes, that is the idea.
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  15. #15
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    Re: Need help with vectos

    I found the answer sheet, it says the answer is (0,2,0) and (0.-4,0)!
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