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Homework Help: Find the locus of a pt in polar form

  1. Nov 3, 2012 #1
    the question is showed below
    i know that x=rcos θ and y= rsinθ and x^2 + y^2 = R^2
    but i just dun know how to find the locus is polar form
    any clue ?

    Attached Files:

    • q.png
      File size:
      26.5 KB
  2. jcsd
  3. Nov 3, 2012 #2
    All you have to do is to find the position of the ring in terms of r and θ.
    It's easy to get r in terms of t and also θ in terms of t.

    That gives you two formulae - you just have to eliminate 't' between them.
  4. Nov 3, 2012 #3
    u mean

    r= (u)t
    θ= (w)t

    rw=uθ and then rw-uθ=0 ??

    actually i have listed this equ but i just don't believe my self
    i feel that i have missed something
  5. Nov 3, 2012 #4
    Ya gotta have faith.

    If you're not sure, draw the locus (path).
    Note that rω = θu can be written as r = kθ where k is a constant - that's easy to plot.
  6. Nov 3, 2012 #5
    the path will be something like a @ ??

    Attached Files:

  7. Nov 3, 2012 #6
  8. Nov 3, 2012 #7
    ya i got it, thx
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