We know that a partial order relation is a relation which is reflexive , antisymmetric and transitive. Example: (x,y) belongs to R iff x=y. For A={1,2,3}, we get R= {(1,1), (2,2), (3,3)}. Now R is reflexive, transitive and also anti-symmetric (if xRy and yRx then x=y).
So equality should be a partial order relation. Is it so? If yes, then why many authors don't mention it as an example of partial order relation. I only find <= , >= , divides, integral multiple and inclusion as an example in most of the books. I am confused.