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Homework Help: I don't get scalar product?

  1. Sep 17, 2009 #1
    1. The problem statement, all variables and given/known data
    Find the scalar product of the 2 vectors.
    Vector A is north of east at 70 degrees with a magnitude of 3.60m
    Vector B is south of west at 30 degrees with a magnitude of 2.40m

    2. Relevant equations

    3. The attempt at a solution
    I did dot product using the formula, 3.60x2.40xcos(-100) and got the wrong answer.. The answer is 13.00. What the hell did I do wrong? I did as the formula said I should do and failed. I don't get it??
    Last edited: Sep 17, 2009
  2. jcsd
  3. Sep 18, 2009 #2


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    Science Advisor
    Homework Helper

    Hi elpermic! :smile:

    It ain't 100. :wink:
  4. Sep 18, 2009 #3

    Doc Al

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    Staff: Mentor

    (1) The formula calls for the angle between the two vectors. That angle is not 100°. (Draw a diagram.)
    (2) The answer cannot be 13.
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