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Math Help - Vector problems

  1. #1
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    Smile Vector problems

    I just started on vector and there are some confusing problems i want to ask:

    Find the magnitude and direction angle of the vector:
    1)  3i-4j<- on this one i found the magnitude but not the direction angle, though i'm positive that i did just like i've done with some previous problems. I got 53.13, but the answer in the book is 306.87

    2) -3i-5j<-- i also got the magnitude of this one, but not the direction angle. again

    3) 7(cos135i+sin135j)

    Find the vector v with the given magnitude and the same direction as u
    |v| = 1, u =<3,-3>
    Please help! Thanks
    Last edited by nhunhu9; July 19th 2010 at 10:54 AM.
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  2. #2
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    Quote Originally Posted by nhunhu9 View Post
    I just started on vector and there are some confusing problems i want to ask:

    Find the magnitude and direction angle of the vector:
    1)  3i-4j<- on this one i found the magnitude but not the direction angle, though i'm positive that i did just like i've done with some previous problems. I got 53.13, but the answer in the book is 306.87

    +i , -j ... quadrant IV angle

    2) -3i-5j<-- i also got the magnitude of this one, but not the direction angle. again

    -i , -j ... quadrant III angle

    3) 7(cos135i+sin135j)

    what is your problem with this vector?

    Find the vector v with the given magnitude and the same direction as u
    |v| = 1, u =<3,-3>

    v = < 1/sqrt(2) , -1/sqrt(2) >
    ...
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  3. #3
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    Number 3 is also find the direction angle but since the fisrt and second problems have to do with quadrant i already firgured it out. Thank you
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