Description: Commutation of restricted and unrestricted existential quantifiers. (Contributed by NM, 12-Apr-2004) (Proof shortened by Andrew Salmon, 8-Jun-2011) (Revised by Thierry Arnoux, 8-Mar-2017)
Ref | Expression | ||
---|---|---|---|
Hypothesis | ralcom4f.1 | ||
Assertion | rexcom4f |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ralcom4f.1 | ||
2 | nfcv | ||
3 | 1 2 | rexcomf | |
4 | rexv | ||
5 | 4 | rexbii | |
6 | rexv | ||
7 | 3 5 6 | 3bitr3i |