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  2. Relation (mathematics) - Wikipedia

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

    In mathematics, a relation denotes some kind of relationship between two objects in a set, which may or may not hold. [1] As an example, " is less than " is a relation on the set of natural numbers ; it holds, for instance, between the values 1 and 3 (denoted as 1 < 3 ), and likewise between 3 and 4 (denoted as 3 < 4 ), but not between the ...

  3. List of trigonometric identities - Wikipedia

    en.wikipedia.org/wiki/List_of_trigonometric...

    These identities are useful whenever expressions involving trigonometric functions need to be simplified. An important application is the integration of non-trigonometric functions: a common technique involves first using the substitution rule with a trigonometric function, and then simplifying the resulting integral with a trigonometric identity.

  4. Functional dependency - Wikipedia

    en.wikipedia.org/wiki/Functional_dependency

    Intuitively, if a functional dependency X → Y holds in R, then the relation can be safely split in two relations alongside the column X (which is a key for () ()) ensuring that when the two parts are joined back no data is lost, i.e. a functional dependency provides a simple way to construct a lossless join decomposition of R in two smaller ...

  5. Binary relation - Wikipedia

    en.wikipedia.org/wiki/Binary_relation

    A function (also called mapping [24]): a binary relation that is functional and total. In other words, every element of the domain has exactly one image element. For example, the red and green binary relations in the diagram are functions, but the blue and black ones are not. An injection: a function that is injective. For example, the green ...

  6. Trigonometry - Wikipedia

    en.wikipedia.org/wiki/Trigonometry

    With these functions, one can answer virtually all questions about arbitrary triangles by using the law of sines and the law of cosines. [33] These laws can be used to compute the remaining angles and sides of any triangle as soon as two sides and their included angle or two angles and a side or three sides are known.

  7. Composition of relations - Wikipedia

    en.wikipedia.org/wiki/Composition_of_relations

    In the mathematics of binary relations, the composition of relations is the forming of a new binary relation R ; S from two given binary relations R and S.In the calculus of relations, the composition of relations is called relative multiplication, [1] and its result is called a relative product.

  8. Transitive relation - Wikipedia

    en.wikipedia.org/wiki/Transitive_relation

    In mathematics, a binary relation R on a set X is transitive if, for all elements a, b, c in X, whenever R relates a to b and b to c, then R also relates a to c.. Every partial order and every equivalence relation is transitive.

  9. Schur orthogonality relations - Wikipedia

    en.wikipedia.org/wiki/Schur_orthogonality_relations

    The space of complex-valued class functions of a finite group G has a natural inner product: , := | | () ¯ where () ¯ denotes the complex conjugate of the value of on g.With respect to this inner product, the irreducible characters form an orthonormal basis for the space of class functions, and this yields the orthogonality relation for the rows of the character table: