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