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Homework Help: Union and Intersection of sets

  1. Feb 3, 2008 #1
    1. The problem statement, all variables and given/known data
    a) Find: [tex]\bigcup_{i=1}^{\infty}} A_i[/tex]

    b) Find: [tex]\bigcap_{i=1}^{\infty}} A_i[/tex]

    Where [itex]A_i[/itex] = (0,i), that is, the set of real numbers x with 0 < x < i

    I was doing okay when they gave me [itex]A_i[/itex] = {i, i+1, i+2, ...}, but now that they're giving me (0,i), and introducing x, I'm getting confused.
  2. jcsd
  3. Feb 3, 2008 #2
    Just noticed that I placed this in the wrong forum. I usually come to the Physics forum, however this time I meant for Calculus.
    Tried to find a way to delete or move it, but not finding a way.

    If an admin finds this, just delete it. I'll post it in the proper forum.

  4. Feb 3, 2008 #3


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    Science Advisor
    Homework Helper

    Try making a picture. Draw a long line, this is the set of all real numbers. We indicate an open interval (a, b) by putting a bracket ( at the point a, and a bracket ) at the point b. Also see this webpage.
    Now draw some intervals (0, 1), (0, 2), (0, 4) and look at their intersection and their union. Post a conjecture about the answer, we'll help you prove it.
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