2.2 Relation

Let A and B be two sets. Then a relation R from A to B is a subset of A×B.

R is a relation from A to B => R is a subset of A×B.

Total number of relations: If A and B are two non empty sets with m and n elements respectively, A×B consists of mn ordered pairs.

Since each subset defines a relation from A to B, so total number of relations from A to B is 2

^{mn}.

2.3 Types of relations

Void relation

Universal relation

Identity relation

Reflexive relation

Symmetric relation

Transitive relation

Antisymmetric relation

Equivalence relation

2.4 (2.5 in the book) Composition of Relations

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