1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook