Relation and function NCERT CHAPTER 2

Relation Let A and B be two non – empty sets. Then, a relation R from A to B is a subset of (A×B) .

Thus , R is a relation from A to B iff R⊆(A×B).

If (a,b)∈R then we say that’a is related to b’ and we write , a R b.

If (a,b)∉R then ‘a is not related to b’ 

DOMAIN OF A RELATION

The set of all first coordinates of elements of R is called the domain of R, written as dom (R) .

RANGE  OF A RELATION

The set of all second coordinates of element of R is called the range of R. dented by range (R).

CO – DOMAIN OF A RELATION

The set B is called the co- domain of R.

Thus, dom (R) = { a : (a,b)⊆R} and 

range (R) = {b : (a,b)⊆R}.

ARROW DIAGRAM 

Let R be a relation from A to B.

Then we draw two bounded figures to denote A and B.

We put dots to represent the elements of A and B.

For each (a,b)∈R, we draw an arrow from a to b.