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Homework Help: Direction cosines and vectors

  1. Sep 12, 2007 #1
    I just started physics this year and having a difficult time, lol.

    anyways, my question is:

    suppose I was given a vector A, and A has x, y, z components of 4,6,3

    How would I find its magnitude of A and the cosines of the angles that makes B?
  2. jcsd
  3. Sep 12, 2007 #2


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    It's like finding the length of a diagonal of a rectangle of length, breadth and depth of 4, 6, and 3 respectively, by the Pythagoras's theorem. And what's B?
  4. Sep 12, 2007 #3
    i'm sorry, I meant what are the angles that make vector A, sorry.
  5. Sep 12, 2007 #4
    also, i'm just wondering why I can't apply the formula Magnitude A = sqrt (x^2, y^2, z^2)
  6. Sep 12, 2007 #5


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    By the way, your "vector" questions are MATH problems.
    There's no physics yet. (Physics is not to blame.)

    Are you looking for the "direction cosines"?
  7. Sep 12, 2007 #6
    I just want to know if I use the |A| = sqrt (x^2 + y^2 + z^3)
  8. Sep 12, 2007 #7
    or the rectangular length like bel has mentioned above.
  9. Sep 12, 2007 #8
    Yep, you can. :smile:
  10. Sep 12, 2007 #9
    hmm, ok thank you guys for the help.
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