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# Lecture - 1 Relations and Functions

**Logics for this lecture: **

Relation \subseteq Cartesian Product

Relation on set A is defined as R \subseteq A \times A

\phi and A \times A are two extreme subsets of A \times A

If R = \phi , then relation is called empty relation.

If R = A \times A , then relation is called universal relation.

Both empty and universal relations are also known as trivial relations.