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Description: Define minus infinity as
the power set of plus infinity. Note that the
definition is arbitrary, requiring only that  be a set not in
 and different
from  (see mnfnre 5469 and pnfnemnf 5509). |
| Ref | Expression |
|---|---|
| df-mnf |
   |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | cmnf 5456 |
. 2
 | |
| 2 | cpnf 5455 |
. . 3
| |
| 3 | 2 | cpw 2391 |
. 2
|
| 4 | 1, 3 | wceq 953 |
1
 |
| Colors of variables: wff set class |
| This definition is referenced by: mnfxr 5466 mnfnre 5469 pnfnemnf 5509 |