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Find polar coordinates (r, θ) of the point.

  1. Mar 26, 2012 #1
    1. The problem statement, all variables and given/known data

    The Cartesian coordinates of a point are given. (3,-5)

    (i) Find polar coordinates (r, θ) of the point, where
    r > 0 and 0 ≤ θ < 2π.
    (ii) Find polar coordinates (r, θ) of the point, where
    r < 0 and 0 ≤ θ < 2π.

    2. Relevant equations

    r^2=x^2+y^2
    tanθ=(y/x) → θ=arctan(y/x)

    3. The attempt at a solution

    r=√(9+25)=√(34)

    θ=arctan(-5/3)

    The problem must be in exact terms which typically involves pi (in the problems I have worked at least). Radians and degrees are not allowed as an answer. What is the value for theta? I can't figure out where to go from there. Any help is appreciated. Thanks!
     
  2. jcsd
  3. Mar 26, 2012 #2

    Office_Shredder

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    If radians and degrees are not allowed as an answer, what units IS your angle supposed to be in? Are you sure you don't mean you simply aren't supposed to submit a decimal approximation to the answer? In this case arctan(-5/3) is the best you can do
     
  4. Mar 26, 2012 #3
    Yes, sorry, that is what I mean. Decimal approximation is not allowed as far as I know and I'm not even aware that leaving it as arctan(-5/3) is allowed. It does not specify, but all the other problems have had pi in the theta value so I have no idea how it is to be submitted. I guess that is more of my own problem than something you guys can help with, but I am unsure on what to do.
     
  5. Mar 26, 2012 #4

    SammyS

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    [itex]\displaystyle -\frac{\pi}{2}<\arctan\left(-\frac{5}{3}\right)<0[/itex]

    You need to get your answer into the correct quadrant.
     
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