RELATIONS
- Relation
A relation is a correspondence between the elements of two sets A and B. A relation
is denoted by the letter R. If x is a member of A and y is a member of B and if x is
related to y then the relation is denoted as x R y.
Eg. : Let A = {2, 5} and B = {4, 6, 8}
The carterian product A x B = {(2, 4) (2, 6) (2, 8) (5, 4) (5, 6) (5, 8)}
If R denotes the relation “is less than” then 2R4 (since 2<4), 2R6, 2R8, 5R6
and 5R8
⇒ R = { (2, 4), (2, 6), (2, 8), (5, 6), (5, 8) }
Thus the set of ordered pairs denote a relation R from A to B.
The idea may be explained orally. Further, the concept of relation using two sets may
be prepared as an embossed diagram and be given to the child to explore.- Reflexive relation
A relation on a set A is said to be reflexive if every element of A is related to itself. In
other words, for all a ∈ A, a R a.
Eg. : In a set of triangles, the relation “is congruent to” is reflexive as every triangle
is congruent to itself.
The idea may be explained orally in addition to the provision of necessary Braille text
material.