Description: Restricted existential quantification over a singleton. (Contributed by Mario Carneiro, 23-Apr-2015) (Revised by NM, 22-Aug-2018)
Ref | Expression | ||
---|---|---|---|
Assertion | rexsns |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | velsn | ||
2 | 1 | anbi1i | |
3 | 2 | exbii | |
4 | df-rex | ||
5 | sbc5 | ||
6 | 3 4 5 | 3bitr4i |