Some help on sets, please!

  1. can anyone tell me the answer to this??

    if
    U (universal set) = {1,2,3,4,5,6,7,8,9,10,11,12,13,14}
    C (just a simple subset of the universal set U)= {1,2,3,4,5}

    then what would be the answer if:

    C U U' ????? (subset C union universal set complement)

    :yuck: thanks !!

    sorry for the double post!! please delete this one!!!
     
  2. jcsd
  3. Don't you need to also include your universe of discourse?

    If your universe of discourse is the natural numbers then,...

    C U U' would be {1,2,3,4,5} U {15,16,17,...}

    If your universe of discourse is the integers then,...

    C U U' would be {... -3,-2,-1,0} U {1,2,3,4,5} U {15,16,17,...}

    For other universes of discourse it could get ugly. :surprise:

    Edited to add the following possibility,...

    If your universe of discourse is U then U' is the empty set so,...

    C U U' would be just be {1,2,3,4,5}
     
    Last edited: Jun 17, 2004
  4. HallsofIvy

    HallsofIvy 40,678
    Staff Emeritus
    Science Advisor

    Neutron star: the original post said "U (universal set) = 1,2,3,4,5,6,7,8,9,10,11,12,13,14}.

    That is the "unverse of discourse".
     
  5. That's normally what I would assume too, but I've found that different people use different notations including college professors and textbook authors. I've seen the term universal set used to refer to a specific set while the author (or professor) continues to treat the problem as though the universe of discourse is still the natural numbers.

    I would agree that they are technically incorrect in doing this. But they seem to do it quite often just the same. I've actually confronted a college professor about this once and all I got in return was a lecture on the difference between a universal set and the universe of discourse.

    Don't look at me. I'm with you! As far as I'm concerned professors and authors who think there is a difference are wrong. But since its an imperfect universe (no pun intended) I like to cover all my bases. :approve:
     
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