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  2. List of set identities and relations - Wikipedia

    en.wikipedia.org/wiki/List_of_set_identities_and...

    3.1 Formulas for binary set operations ⋂, ... which means that all sets that are used in the formula are subsets of . ... (where represents ), might ...

  3. Subset - Wikipedia

    en.wikipedia.org/wiki/Subset

    The set {x: x is a prime number greater than 10} is a proper subset of {x: x is an odd number greater than 10} The set of natural numbers is a proper subset of the set of rational numbers; likewise, the set of points in a line segment is a proper subset of the set of points in a line.

  4. Set (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Set_(mathematics)

    A set of polygons in an Euler diagram This set equals the one depicted above since both have the very same elements.. In mathematics, a set is a collection of different [1] things; [2] [3] [4] these things are called elements or members of the set and are typically mathematical objects of any kind: numbers, symbols, points in space, lines, other geometrical shapes, variables, or even other ...

  5. Indicator function - Wikipedia

    en.wikipedia.org/wiki/Indicator_function

    The indicator or characteristic function of a subset A of some set X maps elements of X to the range {,}. This mapping is surjective only when A is a non-empty proper subset of X . If A ≡ X , {\displaystyle A\equiv X,} then 1 A = 1. {\displaystyle \mathbf {1} _{A}=1.}

  6. Algebra of sets - Wikipedia

    en.wikipedia.org/wiki/Algebra_of_sets

    The algebra of sets is the set-theoretic analogue of the algebra of numbers. Just as arithmetic addition and multiplication are associative and commutative, so are set union and intersection; just as the arithmetic relation "less than or equal" is reflexive, antisymmetric and transitive, so is the set relation of "subset".

  7. Cantor's theorem - Wikipedia

    en.wikipedia.org/wiki/Cantor's_theorem

    The version of this argument he gave in that paper was phrased in terms of indicator functions on a set rather than subsets of a set. [7] He showed that if f is a function defined on X whose values are 2-valued functions on X, then the 2-valued function G(x) = 1 − f(x)(x) is not in the range of f.

  8. Inclusion–exclusion principle - Wikipedia

    en.wikipedia.org/wiki/Inclusion–exclusion...

    An explicit formula for them can be obtained by applying the principle of inclusion–exclusion to a very closely related problem, namely, counting the number of partitions of an n-set into k non-empty but distinguishable boxes (ordered non-empty subsets). Using the universal set consisting of all partitions of the n-set into k (possibly empty ...

  9. Element (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Element_(mathematics)

    As a relation, set membership must have a domain and a range. Conventionally the domain is called the universe denoted U. The range is the set of subsets of U called the power set of U and denoted P(U). Thus the relation is a subset of U × P(U). The converse relation is a subset of P(U) × U.