Question

4. (15 pts) Suppose that R and S are reflexive relations on a set A. Prove or disprove each of these statements. (Note that RI R2 consists of all ordered pairs (a, b), where student a has taken course b but does not need it to graduate or needs course b to graduate but has not taken it.) a) R U S is reflexive. b) R S is reflexive. c) R田s is irreflexive. d) R- S is irreflexive. e) S。R is reflexive.

Answer 1

4. Since R and s ar2 dnd (a,a) s Hence Rus is a ROSis als o Now Since C*, R S is not