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Homework Help: Equation of a cylinder

  1. May 25, 2010 #1
    1. In Murray Spiegel's Advanced Calculus, in solved problem 10.18 he describes a cylinder as having equation x^2 + y^2 = ax. Surely this equation is for a 2-D object. Whats going on as a cylinder is 3D?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 25, 2010 #2


    Staff: Mentor

    No, it's a 3D object, with z being arbitrary. If you look at the trace of this cylinder in the x-y plane (i.e., z = 0), you get a circle. For any z = k, some constant, you also get a circle, but this time in the plane z = k.
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