Relation:
If A and B are two non empty sets then any subset of A X B is called a relation from A to B
Representation of a relation
1.Roster form. In this form, a relation is represented by the set of all ordered pairs which belong to the given
relation. For example, let A= (1, 2, 3, 4, 5) and B (1, 2, 3, 4,, 20), and let R be the relation has as its square'
from A to B, then R= ((1, 1), (2, 4), (3, 9), (4, 16)).
2.Set-builder form. In this form, the relation is represented as {(x, y): x ϵA, y ϵB, x... Y}, the blank is to be
replaced by the rule which associates x and y.
3.By arrow (ray) diagram. In this form, the relation is represented by drawing arrows (rays) from first
components to the second components of all ordered pairs which belong to the given relation.
Domain and range of a relation
Let A, B be any two (non-empty) sets and R be a relation from A to B, then the domain of the relation R, is the
set of all first components of the ordered pairs which belong to R, and the range of the relation R is the of all
second components of the ordered pairs which belong to R.
If R is a relation from A to B then B is called codomain of R