Description: Obsolete version of 1n0 as of 10-Jun-2026. (Contributed by NM, 26-Dec-2004) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | 1n0OLD | |- 1o =/= (/) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df1o2 | |- 1o = { (/) } |
|
| 2 | 0ex | |- (/) e. _V |
|
| 3 | 2 | snnz | |- { (/) } =/= (/) |
| 4 | 1 3 | eqnetri | |- 1o =/= (/) |