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Vector Problem

  1. Sep 20, 2009 #1
    1. The problem statement, all variables and given/known data

    Vectors A and B have equal magnitudes of 5.12. If the sum of A and B is the vector 6.37j, determine the angle between A and B.

    2. Relevant equations

    Cosine law?

    3. The attempt at a solution

    I attempted to do this using the cosine law which I thought made sense but 103 degrees is not the right answer..
     
  2. jcsd
  3. Sep 20, 2009 #2
    when i use the cosine equation:
    cosA = (b^2 +c^2 - a^2)/2bc
    A = cos-1[(b^2 +c^2 - a^2)/2bc]
    i did not get 103 degrees... id suggest to check your numbers??
     
  4. Sep 20, 2009 #3
    You got 77 degrees correct?
    I just subtracted from 180 because the angle I assume is tail to tail.

    I also tried 77 degrees (or rather 76.9 degrees) and it's also not the answer.
     
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