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Homework Help: Parametric equation

  1. Jun 10, 2008 #1
    1. The problem statement, all variables and given/known data
    Describe motion of a particle w/ position xy


    2. Relevant equations

    x=cospi(t) y=sinpi(t)

    3. The attempt at a solution
    solving for t
    t=x/cospi
    so y=sinpi(x)/cospi
    y=tanpi(x)

    interval=at least one at most 2
    since tan(x)=0 at pi and 2pi
    and this is where the boundaries are so the particle travels from pi and 2pi counterclockwise
    but the textbook has a different (but reasonable) answer in that it squares cos pi and
    sin pi to equal 1 and uses the circle equation but ends up with the same diagram and
    direction. If I went wrong, can you please tell me where I went wrong since my answer
    seems legit to me.
     
  2. jcsd
  3. Jun 10, 2008 #2
    x= cos[tex]\pi[/tex]t
    should become
    t=[tex]cos^{-1}x[/tex]/[tex]\pi[/tex]
     
  4. Jun 10, 2008 #3

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    have some π …

    Hi evilpostingmong! :smile:

    Your initial equations are wrong.

    It isn't x=cosπ(t) y=sinπ(t);

    it's x=cos(πt) y=sin(πt).

    Now try! :smile:

    (oh … and here's some π and other things to pack in your bag …)
     
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