Description: In a null graph (with no vertices), all closed neighborhoods are empty. (Contributed by AV, 15-Nov-2020)
Ref | Expression | ||
---|---|---|---|
Assertion | clnbgr0vtx |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nel02 | ||
2 | df-nel | ||
3 | 1 2 | sylibr | |
4 | eqid | ||
5 | 4 | clnbgrnvtx0 | |
6 | 3 5 | syl |