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  1. general topology - Infinite compact subset of $\mathbb {Q ...

    Nov 6, 2013 · In fact, more is known: Theorem: Every (Hausdorff) countable compact is homeomorphic to a subspace of Q Q. Essentially, it is a consequence of Sierpinski …

  2. What is infinity divided by infinity? - Mathematics Stack Exchange

    Aug 11, 2012 · I know that $\\infty/\\infty$ is not generally defined. However, if we have 2 equal infinities divided by each other, would it be 1? if we have an infinity divided by another half-as …

  3. Associativity of infinite matrix product. - Mathematics Stack …

    Many texts reads "It is well known that for infinite matrices multiplication is non-associative". A treatise on this can be found in On the associativity of infinite matrix multiplication. However...

  4. Is there a shape with infinite volume but finite surface area?

    Mar 28, 2023 · Is there any pathological shape that has a finite surface area but an infinite volume, sort of like the opposite of a Gabriel's horn?

  5. real analysis - Prove that an infinite sigma algebra contains an ...

    Jan 2, 2015 · I am wondering if we just showed that any infinite set of sets contains an infinite restriction. So that the sigma algebra component isn't needed for the next iteration.

  6. Infinite intersection of open sets - Mathematics Stack Exchange

    Oct 2, 2015 · Similarly, to disprove infinite intersection of open sets is open, it is enough to give a particular collection of open sets such that intersection is not open.

  7. discrete mathematics - Countably Infinite, Uncountable or Finite ...

    Dec 5, 2015 · I am having trouble with the following terms: countably infinite, uncountable, and finite. In addition, for the following problems I need to select which category they fall into. $1)$ …

  8. Uncountable vs Countable Infinity - Mathematics Stack Exchange

    Nov 5, 2015 · My friend and I were discussing infinity and stuff about it and ran into some disagreements regarding countable and uncountable infinity. As far as I understand, the list of …

  9. Partitioning an infinite set - Mathematics Stack Exchange

    Dec 1, 2010 · Can you partition an infinite set, into an infinite number of infinite sets?

  10. I have learned that 1/0 is infinity, why isn't it minus infinity?

    An infinite number? Kind of, because I can keep going around infinitely. However, I never actually give away that sweet. This is why people say that 1 / 0 "tends to" infinity - we can't really use …