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  2. Cantor's diagonal argument - Wikipedia

    en.wikipedia.org/wiki/Cantor's_diagonal_argument

    In which case, if P 1 (S) is the set of one-element subsets of S and f is a proposed bijection from P 1 (S) to P(S), one is able to use proof by contradiction to prove that |P 1 (S)| < |P(S)|. The proof follows by the fact that if f were indeed a map onto P ( S ), then we could find r in S , such that f ({ r }) coincides with the modified ...

  3. Uncountable set - Wikipedia

    en.wikipedia.org/wiki/Uncountable_set

    The best known example of an uncountable set is the set ⁠ ⁠ of all real numbers; Cantor's diagonal argument shows that this set is uncountable. The diagonalization proof technique can also be used to show that several other sets are uncountable, such as the set of all infinite sequences of natural numbers ⁠ ⁠ (see: (sequence A102288 in the OEIS)), and the set of all subsets of the set ...

  4. Aleph number - Wikipedia

    en.wikipedia.org/wiki/Aleph_number

    The set ω 1 is itself an ordinal number larger than all countable ones, so it is an uncountable set. Therefore, ℵ 1 is distinct from ℵ 0. The definition of ℵ 1 implies (in ZF, Zermelo–Fraenkel set theory without the axiom of choice) that no cardinal number is between ℵ 0 and ℵ 1.

  5. Cantor's first set theory article - Wikipedia

    en.wikipedia.org/wiki/Cantor's_first_set_theory...

    Cantor's article is short, less than four and a half pages. [A] It begins with a discussion of the real algebraic numbers and a statement of his first theorem: The set of real algebraic numbers can be put into one-to-one correspondence with the set of positive integers. [3]

  6. Vitali set - Wikipedia

    en.wikipedia.org/wiki/Vitali_set

    In mathematics, a Vitali set is an elementary example of a set of real numbers that is not Lebesgue measurable, found by Giuseppe Vitali in 1905. [1] The Vitali theorem is the existence theorem that there are such sets. Each Vitali set is uncountable, and there are uncountably many Vitali sets. The proof of their existence depends on the axiom ...

  7. Mathematical proof - Wikipedia

    en.wikipedia.org/wiki/Mathematical_proof

    [1] A mathematical proof is a deductive argument for a mathematical ... Daoud, A. (2011), Proof in Mathematics: An Introduction, Kew Books, ISBN 978-0-646-54509-7.

  8. List of mathematical proofs - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_proofs

    Bertrand's postulate and a proof; Estimation of covariance matrices; Fermat's little theorem and some proofs; Gödel's completeness theorem and its original proof; Mathematical induction and a proof; Proof that 0.999... equals 1; Proof that 22/7 exceeds π; Proof that e is irrational; Proof that π is irrational

  9. Strong measure zero set - Wikipedia

    en.wikipedia.org/wiki/Strong_measure_zero_set

    In mathematical analysis, a strong measure zero set [1] is a subset A of the real line with the following property: for every sequence (ε n) of positive reals there exists a sequence (I n) of intervals such that |I n | < ε n for all n and A is contained in the union of the I n. (Here |I n | denotes the length of the interval I n.)