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Homework Help: Problem with physics points

  1. Jul 10, 2006 #1
    Given n points n1,...,nk in the xy-plane, is it always possible to find a point p such that d(ni,p) is rational for 0<i<k+1?
  2. jcsd
  3. Jul 10, 2006 #2


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    What if one point is (x1,0), with x1 rational, and the other is (x2,0), with x2 irrational?
  4. Jul 10, 2006 #3
    Draw a line segment AB between (x1,0) and (x2,0) and a line L bisecting the line segment AB perpenticularly.
  5. Jul 10, 2006 #4
    um....either I'm misinterpreting the OP or the answer can be seen by drawing a circle radius p/q (where p/q is rational) around any of the points (with the point as the center).
  6. Jul 10, 2006 #5


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    Perhaps you are misinterpreting. The question was whether, given a finite set of points, there exist a point p such that its distance to every point in the set is rational. Certainly every point on the circumference of your circle has rational distance (p/q) from the center, but what about the other points in the set?
  7. Jul 10, 2006 #6
    I've tried everything I know. I don't know how to produce an answer.
  8. Jul 10, 2006 #7


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    Was this given to you as an assignment, or did you just think of it yourself? It may be a much deeper question than it appears.
  9. Jul 10, 2006 #8
    A friend sent this 'funny problem' that he got from a 'funny book'. I brought it to the canadian undergraduate math conference last week and everyone was stumped.

    EDIT: Oh and d is the Euclidean metric. No cheating.
    Last edited: Jul 10, 2006
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