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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. For example, less than and equality among real numbers are both transitive: If a < b and b < c then a < c; and if x ...
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.
An element y is called (simply) an inverse of x if xyx = x and y = yxy. Every regular element has at least one inverse: if x = xzx then it is easy to verify that y = zxz is an inverse of x as defined in this section. Another easy to prove fact: if y is an inverse of x then e = xy and f = yx are idempotents, that is ee = e and ff = f.
In a vector space, the additive inverse −v (often called the opposite vector of v) has the same magnitude as v and but the opposite direction. [11] In modular arithmetic, the modular additive inverse of x is the number a such that a + x ≡ 0 (mod n) and always exists. For example, the inverse of 3 modulo 11 is 8, as 3 + 8 ≡ 0 (mod 11). [12]
An element x is called invertible if there exists an element y such that x • y = e and y • x = e. The element y is called the inverse of x. Inverses, if they exist, are unique: if y and z are inverses of x, then by associativity y = ey = (zx)y = z(xy) = ze = z. [6] If x is invertible, say with inverse y, then one can define negative powers ...
An nth root of unity is a complex number whose nth power is 1, a root of the polynomial x n − 1. The set of all n th roots of unity forms a cyclic group of order n under multiplication. [ 1 ] The generators of this cyclic group are the n th primitive roots of unity ; they are the roots of the n th cyclotomic polynomial .
The "angle" y is hyperbolic angle, slope, or circular angle according to the host ring. Linear fractional transformations are shown to be conformal maps by consideration of their generators: multiplicative inversion z → 1/z and affine transformations z → az + b. Conformality can be confirmed by showing the generators are all conformal.
In the monoid of binary endorelations on a set (with the binary operation on relations being the composition of relations), the converse relation does not satisfy the definition of an inverse from group theory, that is, if is an arbitrary relation on , then does not equal the identity relation on in general.