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Homework Help: Coordinates physics homework

  1. Jan 17, 2008 #1
    1. The problem statement, all variables and given/known data

    The rectangular and polar coordinates of a point are (x,y) and (r,theta) where x = 7 and theta = 52 degrees. Determine r and y.

    2. Relevant equations

    r = srt(x^2 + y^2)
    theta = arctan(y/x)
    x = rcos(theta)
    y = rsin(theta)

    3. The attempt at a solution

    I tried to assume that r and x would be the same, so I let r = 7, which would then make y = 5.5. But that's wrong. What else can possibly be done?
    Last edited: Jan 17, 2008
  2. jcsd
  3. Jan 17, 2008 #2
    2 equations, 2 unknowns

    x=rcos(theta) eqn. 1
    y=rsin(theta) eqn. 2

    Since you know what x and theta are you can solve for r in eqn. 1.

    Then once you know r you can plug that into eqn. 2 and solve for y.
  4. Jan 17, 2008 #3
    Haha, nice. I was having one of those mental blocks that just would not allow me to think of that. Thanks.
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