Description: Define the class of reflexive relations. This is practically dfrefrels2 (which reveals that RefRels can not include proper classes like _I as is elements, see comments of dfrefrels2 ).
Another alternative definition is dfrefrels3 . The element of this class and the reflexive relation predicate ( df-refrel ) are the same, that is, ( R e. RefRels <-> RefRel R ) when A is a set, see elrefrelsrel .
This definition is similar to the definitions of the classes of symmetric ( df-symrels ) and transitive ( df-trrels ) relations. (Contributed by Peter Mazsa, 7-Jul-2019)
Ref | Expression | ||
---|---|---|---|
Assertion | df-refrels | ⊢ RefRels = ( Refs ∩ Rels ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
0 | crefrels | ⊢ RefRels | |
1 | crefs | ⊢ Refs | |
2 | crels | ⊢ Rels | |
3 | 1 2 | cin | ⊢ ( Refs ∩ Rels ) |
4 | 0 3 | wceq | ⊢ RefRels = ( Refs ∩ Rels ) |