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Homework Help: Polar coordinates question

  1. Jun 15, 2010 #1
    1. The problem statement, all variables and given/known data
    Convert to an equation in polar coordinates y = x^(2)

    2. Relevant equations
    x = r cos (theta) , y = r sin (theta) , tan (theta) = y/x

    3. The attempt at a solution
    Here is my work so far: y=x^(2) so r sin (theta) = (r cos (theta))^2 and r sin (theta) = r^(2) cos^(2) theta. I'm not sure how to move the r's to one side of the equation though. Can I apply tan (theta) = y/x or ? Thanks in advance!
  2. jcsd
  3. Jun 15, 2010 #2


    Staff: Mentor

    You can divide both sides of your equation by r to get sin(theta) = rcos^2(theta). It's not always legitimate to do this, as you might be losing solutions for r = 0. In this case, r = 0 is still a solution.
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