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Homework Help: Question about the direction of a vector

  1. May 16, 2016 #1
    1. The problem statement, all variables and given/known data
    Let A= 3i - 6j and B= 4i - 5j. The direction of the vector C = A - B is at an angle of?

    2. Relevant equations
    Magnitude= ( a^2 + b^2 ) ^1/2
    Tan^-1 = b/a

    3. The attempt at a solution
    A-B =
    3-4 i -6--5j
    -1i -1j
    Tan^-1 = -1/-1 = 45
    45+180 = 225

    Is this correct?
  2. jcsd
  3. May 16, 2016 #2


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    You really need to work on your notation here, the first line is missing parentheses or basis vectors for two terms, there is no equality sign between the second line and the third line, the inverse tangent function has no argument and -1/-1 is 1 and not 45.

    That being said, what you are actually doing (which is not what you are writing) is correct.
  4. May 18, 2016 #3


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    As this is a 2D problem it's not hard to draw it.
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