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Homework Help: Vectors and displacement.

  1. Jan 16, 2010 #1
    1. The problem statement, all variables and given/known data
    A map suggests that Atlanta is 728 mi in a direction of 4.80° north of east from Dallas. The same map shows that Chicago is 561 miles in a direction of 20.8° west of north from Atlanta. Modeling the Earth as flat, use this information to find the displacement from Dallas to Chicago.

    magnitude _______Miles
    2. Relevant equations

    R = Sqrt (A^2+B^2 - 2(A)(B)(cos(theta)))

    3. The attempt at a solution

    I ended up getting 817 as my answer, the site kept saying its within 10% of the correct answer, but I may have rounded wrong. I didn't round until the very last part.
  2. jcsd
  3. Jan 16, 2010 #2
    resolve them into two vectors
    then use vector addition
    finally take the magnitude of the vector

    i get an answer way off yours
  4. Jan 17, 2010 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    That equation should work. I used it and got a different answer, but within 10% of yours.

    What are you using for theta?
  5. Jan 19, 2010 #4
    i didnt use your formula
    and the formula you are trying to use is not right
    it should be
    R = Sqrt (A^2+B^2 + 2(A)(B)(cos(theta)))
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