Description: Alternate definition of the empty set. (Contributed by NM, 25-Mar-2004) (Proof shortened by BJ, 23-Sep-2024)
Ref | Expression | ||
---|---|---|---|
Assertion | dfnul3 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | fal | ||
2 | pm3.24 | ||
3 | 1 2 | 2false | |
4 | 3 | abbii | |
5 | dfnul4 | ||
6 | df-rab | ||
7 | 4 5 6 | 3eqtr4i |