Description: A unique existential quantifier restricted to the universe is unrestricted. (Contributed by NM, 1-Nov-2010)
Ref | Expression | ||
---|---|---|---|
Assertion | reuv | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-reu | |
|
2 | vex | |
|
3 | 2 | biantrur | |
4 | 3 | eubii | |
5 | 1 4 | bitr4i | |