Description: The interior of the empty set. (Contributed by NM, 2-Oct-2007)
Ref | Expression | ||
---|---|---|---|
Assertion | ntr0 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0opn | |
|
2 | 0ss | |
|
3 | eqid | |
|
4 | 3 | isopn3 | |
5 | 2 4 | mpan2 | |
6 | 1 5 | mpbid | |