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Homework Help: Equation of surface

  1. Jul 14, 2011 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    3. The attempt at a solution

    It seems very obvious that after rotation, it becomes a circle, so how to write it out mathematically?

    That I don't know the general equation of a surface.
    Is [itex]y^2+x^2=f^2(x)[/itex] the answer?


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  2. jcsd
  3. Jul 14, 2011 #2
    Yes, this is the general equation for a circle


    As seen in the figure, f(x)=radius

    And from polar coordinates you can get the equation:

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