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Homework Help: Determining the field lines

  1. Mar 27, 2012 #1
    1. The problem statement, all variables and given/known data

    Determine the field lines of the vector field f: R^3 --> R^3 defined by

    f(x,y,z) = (x/(1+z2) , y/(x2+y2) , 0)

    2. Relevant equations

    3. The attempt at a solution

    I know that my vector field is:

    F(x,y,z) = (x/((1+z^2)*(x^2+y^2))*i + (y/((1+z^2)*(x^2+y^2))*j + 0k

    I choose the point (1,1,1) and if I put that into F(1,1,1) I get

    (1/8)i + (1/8)j + 0*k --> <1/8, 1/8>

    I need a 3D graph right?

    Well, first of all, I dont know how to plot (1/8,1/8) into a 3D graph. Second of all, what happens to the z-coordinate?
    Third: I want more than one vector obviously, but when I try with (1,1,-1) I get ∞, which I cannot use to make a vector. Which coordinates can I use?
  2. jcsd
  3. Mar 29, 2012 #2
    i would like to know this as well
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