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Homework Help: Short question about sets

  1. Sep 30, 2011 #1
    1. The problem statement, all variables and given/known data

    Suppose A = {1,{1},{1,{1}}}

    Then is {{{1}}} an element of A?

    3. The attempt at a solution

    I am thinking A has the elements are only 1, {1}, {1, {1}}

    But {{{1}}} has only the element {{1}}

    While A has the element {1,{1}}, you can't just take out the element 1 from {1,{1}}

    So many brackets LOL
  2. jcsd
  3. Sep 30, 2011 #2


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    No, it's not in A. You can see the three elements of A. {{{1}}} definitely isn't one of them. Haven't we been through this sort of thing before?
  4. Sep 30, 2011 #3
    No that time was confusing subsets and elements

    Like (last time) I couldn't figure out why {1} isn't a subset of some set (which I will call B) B = {{1},2,3}
  5. Sep 30, 2011 #4
    thank you by the way! (this shouldn't even be in calculus and beyond LOL, I don't know why I posted it here)
  6. Sep 30, 2011 #5


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    Ok, new confusion then. So what is it this time? {1,{1}} has two elements 1 and {1}. {{{1}}} has one element {{1}}. Why would you think they could be the same?
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