Description: An indexed union of the empty set is empty. (Contributed by NM, 26-Mar-2003) (Proof shortened by Andrew Salmon, 25-Jul-2011)
Ref | Expression | ||
---|---|---|---|
Assertion | iun0 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | noel | |
|
2 | 1 | a1i | |
3 | 2 | nrex | |
4 | eliun | |
|
5 | 3 4 | mtbir | |
6 | 5 | nel0 | |