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Vector Addition? Which Vectors Do I Draw and Where?

  1. Feb 6, 2013 #1
    1. The problem statement, all variables and given/known data
    Vectors a and b have magnitudes 2 and 3. The angle between them is 50 degrees. Determine 5a - 2b and determine its magnitude and direction


    2. Relevant equations
    Cosine Law and Sine Law



    3. The attempt at a solution
    I can solve for the magnitude using the cos law and obtain an answer of 7.67 which is correct, however the direction and angle looks as if which vector i draw and where I draw it Heres a picture (The magnitudes I have just labelled as 10 which is 5a and 6 for 2b) :

    Untitled_zpsd4cc7bd5.png

    Which drawing should I use, because It results in me getting different angles and direction
     
  2. jcsd
  3. Feb 6, 2013 #2

    tms

    User Avatar

    The most straightforward approach would be to pick one vector as the x axis, then break the other into its component, and add them that way.
     
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