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A symmetric relation is a type of binary relation. Formally, a binary relation R over a set X is symmetric if: [1], (), where the notation aRb means that (a, b) ∈ R. An example is the relation "is equal to", because if a = b is true then b = a is also true.
For example, "is a blood relative of" is a symmetric relation, because x is a blood relative of y if and only if y is a blood relative of x. Antisymmetric for all x, y ∈ X, if xRy and yRx then x = y. For example, ≥ is an antisymmetric relation; so is >, but vacuously (the condition in the definition is always false). [11] Asymmetric
For symmetric difference, the sets ( ) and () = ( ) are always disjoint. So these two sets are equal if and only if they are both equal to ∅ . {\displaystyle \varnothing .} Moreover, L ∖ ( M R ) = ∅ {\displaystyle L\,\setminus \,(M\,\triangle \,R)=\varnothing } if and only if L ∩ M ∩ R = ∅ and L ⊆ M ∪ R . {\displaystyle L\cap M ...
Generalizing from geometrical symmetry in the previous section, one can say that a mathematical object is symmetric with respect to a given mathematical operation, if, when applied to the object, this operation preserves some property of the object. [15] The set of operations that preserve a given property of the object form a group.
Symmetry occurs not only in geometry, but also in other branches of mathematics. Symmetry is a type of invariance: the property that a mathematical object remains unchanged under a set of operations or transformations. [1] Given a structured object X of any sort, a symmetry is a mapping of the object onto itself which preserves the structure.
When a commutative operation is written as a binary function = (,), then this function is called a symmetric function, and its graph in three-dimensional space is symmetric across the plane =. For example, if the function f is defined as f ( x , y ) = x + y {\displaystyle f(x,y)=x+y} then f {\displaystyle f} is a symmetric function.
In mathematics, the symmetric closure of a binary relation on a set is the smallest symmetric relation on that contains .. For example, if is a set of airports and means "there is a direct flight from airport to airport ", then the symmetric closure of is the relation "there is a direct flight either from to or from to ".
For example, that every equivalence relation is symmetric, but not necessarily antisymmetric, is indicated by in the "Symmetric" column and in the "Antisymmetric" column, respectively. All definitions tacitly require the homogeneous relation R {\displaystyle R} be transitive : for all a , b , c , {\displaystyle a,b,c,} if a R b {\displaystyle ...