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Homework Help: What is the angle theta between vectors

  1. Apr 1, 2010 #1
    1. The problem statement, all variables and given/known data
    What is the angle theta between vectors vec A and vec B if vec A = 4 -3 and
    vec B = -2 + 5?


    2. Relevant equations
    arccos((a dot b)/(|a||b|))


    3. The attempt at a solution

    4*-2+-3*5=-23
    sqrt(4^2+-3^2)*sqrt(-2^2+5^2)=10.39

    arc
    not sure what i am doing wrong but thats the equation i found online and i keep getting undefined when i plug it into my calculator
     
    Last edited: Apr 1, 2010
  2. jcsd
  3. Apr 1, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Show what you plugged in.
     
  4. Apr 1, 2010 #3
    edited the question, but sorry i realized my error, had a mistake in the magnitudes, got the problem right
     
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