Description: The zero subspace is a proper subset of nonzero Hilbert lattice elements. (Contributed by NM, 9-Jun-2004) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | ch0pss | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | df-pss | ||
| 2 | necom | ||
| 3 | ch0le | ||
| 4 | 3 | biantrurd | |
| 5 | 2 4 | bitr3id | |
| 6 | 1 5 | bitr4id |