Description: The empty set is not a positive real. (Contributed by NM, 15-Nov-1995) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | 0npr | |- -. (/) e. P. |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid | |- (/) = (/) |
|
2 | prn0 | |- ( (/) e. P. -> (/) =/= (/) ) |
|
3 | 2 | necon2bi | |- ( (/) = (/) -> -. (/) e. P. ) |
4 | 1 3 | ax-mp | |- -. (/) e. P. |