Description: The empty set is not a signed real. (Contributed by NM, 25-Aug-1995) (Revised by Mario Carneiro, 10-Jul-2014) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | 0nsr |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid | ||
2 | enrer | ||
3 | erdm | ||
4 | 2 3 | ax-mp | |
5 | elqsn0 | ||
6 | 4 5 | mpan | |
7 | df-nr | ||
8 | 6 7 | eleq2s | |
9 | 8 | necon2bi | |
10 | 1 9 | ax-mp |