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Homework Help: Magnetic vectors

  1. Apr 16, 2010 #1
    1. The problem statement, all variables and given/known data
    For the two vectors in the figure , find the magnitude of the vector product lAl x lBl.
    http://session.masteringphysics.com/problemAsset/1040325/3/yf_Figure_1_29.jpg

    2. Relevant equations
    lAl*lBl=lAl*lBlsin(alpha)


    3. The attempt at a solution

    2.8cm * 1.9cm * cos(60) = 2.66cm^2

    2.8cm * 1.9cm * cos(120) = -2.66cm^2

    Since they made two 60 degree, I thought the alpha was 60 but I got wrong.

    Then, I came up with the 120 degree, however it is also wrong.

    Where did I do wrong?

    Please help me..
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 17, 2010 #2

    ehild

    User Avatar
    Homework Helper

    Why do you use cosine 120 degrees instead of sine?

    ehild
     
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