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  2. Union (set theory) - Wikipedia

    en.wikipedia.org/wiki/Union_(set_theory)

    In set theory, the union (denoted by ∪) of a collection of sets is the set of all elements in the collection. [1] It is one of the fundamental operations through which sets can be combined and related to each other. A nullary union refers to a union of zero (⁠ ⁠) sets and it is by definition equal to the empty set.

  3. Intersection number - Wikipedia

    en.wikipedia.org/wiki/Intersection_number

    The complexity enters when calculating intersections at points of tangency, and intersections which are not just points, but have higher dimension. For example, if a plane is tangent to a surface along a line, the intersection number along the line should be at least two. These questions are discussed systematically in intersection theory.

  4. List of set identities and relations - Wikipedia

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

    This article lists mathematical properties and laws of sets, involving the set-theoretic operations of union, intersection, and complementation and the relations of set equality and set inclusion. It also provides systematic procedures for evaluating expressions, and performing calculations, involving these operations and relations.

  5. Intersection (set theory) - Wikipedia

    en.wikipedia.org/wiki/Intersection_(set_theory)

    The number 9 is not in the intersection of the set of prime numbers ... Intersection distributes over union and union distributes over intersection. That is, ...

  6. Algebra of sets - Wikipedia

    en.wikipedia.org/wiki/Algebra_of_sets

    The union and intersection of sets may be seen as analogous to the addition and multiplication of numbers. Like addition and multiplication, the operations of union and intersection are commutative and associative, and intersection distributes over union. However, unlike addition and multiplication, union also distributes over intersection.

  7. Naive set theory - Wikipedia

    en.wikipedia.org/wiki/Naive_set_theory

    The intersection of A ... is a Boolean algebra under the operations of union and intersection. ... is also used to denote an open interval on the real number line, ...

  8. Cardinality - Wikipedia

    en.wikipedia.org/wiki/Cardinality

    7 Union and intersection. 8 ... Cardinal arithmetic can be used to show not only that the number of points in a real number line is equal to the number of ...

  9. Line–line intersection - Wikipedia

    en.wikipedia.org/wiki/Lineline_intersection

    The intersection point falls within the first line segment if 0 ≤ t ≤ 1, and it falls within the second line segment if 0 ≤ u ≤ 1. These inequalities can be tested without the need for division, allowing rapid determination of the existence of any line segment intersection before calculating its exact point.