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How to use arc tan to find an angle?

  1. Sep 28, 2011 #1
    in physics we were doing a problem that essentially involved vectors and in the end we were left with 2 displacements. how would i find the angle between them if it was not a right triangle? i asked someone and they said that i could find it using artan(Ry/Rx) ...R being one of the displacements
     
  2. jcsd
  3. Sep 28, 2011 #2

    HallsofIvy

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    If Ry and Rx are the y and x components of a vector, then there is a right angle between them- the x and y axes are at right angles. So, yes, Arctan(Ry/Rx) is the angle the vector makes with the positive x axis. (Since tangent is periodic, arctan is multivalued. Arctan is the "principal" value between -90 and 90 degrees. Make sure that is what you want.)
     
  4. Sep 28, 2011 #3
    so if the R value is 218.684158367 and the other displacement is 187 how would i find the angle between them using the arc tan?
     
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