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Homework Help: Limit point.

  1. Feb 7, 2012 #1
    1. The problem statement, all variables and given/known data
    a)Determine at least three limit points for the set {sin(n): n a positive integer}
    b)How many limit points does the set {sin(n): n a positive integer} have?
    3. The attempt at a solution
    For a it seems that it wouldn't have a limit point because sin(n) would not converge to anything. On the other hand maybe its obvious and maybe 3 limit points would be
    sin(1), sin(2), sin(3) , now that I think about it, it seems like a tricky question.
    for part b, if sin(n) has 3 limit points then it seems like the set would have an infinite amount of points.
  2. jcsd
  3. Feb 7, 2012 #2
    From http://en.wikipedia.org/wiki/Limit_point we have that x is a limit point of A={sin(n): n a positive integer} if every neighborhood of x has another element of A different from x. So if you can show that you can approximate x as closely as you wish with elements taken from A, then you have a limit point there. I think three natural points to try to show are limit points are 0,1,-1.
  4. Feb 8, 2012 #3
    so really and point in [-1,1] should be a limit point because i can get as close as I want to any point in there with the sin(n), can points in my set {sin(n)} where n is a natural number.
    be a limit point?
    Last edited: Feb 8, 2012
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