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Homework Help: Changing rectangular to cylindrical

  1. Nov 12, 2011 #1
    Change (-3,3,3) to cylindrical coordinates.
    I'm doing r^2 = x^2 + y^2, which I find r = sqrt(18) = 3radical(2)
    tan(theta) = 3/-3 = 1, so theta = -pi/4 = 7pi/4.
    z = 3
    Cylindrical coordinates are (3sqrt(2),7pi/4,3).
    Is this right? Correct answer to the homework says 3pi/4 for the angle, for some reason.
  2. jcsd
  3. Nov 12, 2011 #2


    Staff: Mentor

    The angle θ is in the 2nd quadrant, so 3[itex]\pi[/itex]/4 is correct.
    In the future, when you post a question, use the three-part template.
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