Description: The union of two sets is a set. Corollary 5.8 of TakeutiZaring p. 16. (Contributed by NM, 1-Jul-1994)
Ref | Expression | ||
---|---|---|---|
Hypotheses | unex.1 | |
|
unex.2 | |
||
Assertion | unex | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | unex.1 | |
|
2 | unex.2 | |
|
3 | 1 2 | unipr | |
4 | prex | |
|
5 | 4 | uniex | |
6 | 3 5 | eqeltrri | |