Description: A pair of an empty set (of edges) and a second set (of vertices) is a trail iff the second set contains exactly one vertex. (Contributed by Alexander van der Vekens, 30-Oct-2017) (Revised by AV, 7-Jan-2021) (Revised by AV, 30-Oct-2021)
Ref | Expression | ||
---|---|---|---|
Hypothesis | 0wlk.v | |
|
Assertion | 0trl | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0wlk.v | |
|
2 | 1 | 0wlk | |
3 | 2 | anbi1d | |
4 | istrl | |
|
5 | funcnv0 | |
|
6 | 5 | biantru | |
7 | 3 4 6 | 3bitr4g | |