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| Mirrors > Home > MPE Home > Th. List > mnfxr | Structured version Visualization version Unicode version | ||
| Description: Minus infinity belongs to the set of extended reals. (Contributed by NM, 13-Oct-2005.) (Proof shortened by Anthony Hart, 29-Aug-2011.) (Proof shortened by Andrew Salmon, 19-Nov-2011.) |
| Ref | Expression |
|---|---|
| mnfxr |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-mnf 10077 |
. . . . 5
| |
| 2 | pnfex 10093 |
. . . . . 6
| |
| 3 | 2 | pwex 4848 |
. . . . 5
|
| 4 | 1, 3 | eqeltri 2697 |
. . . 4
|
| 5 | 4 | prid2 4298 |
. . 3
|
| 6 | elun2 3781 |
. . 3
| |
| 7 | 5, 6 | ax-mp 5 |
. 2
|
| 8 | df-xr 10078 |
. 2
| |
| 9 | 7, 8 | eleqtrri 2700 |
1
|
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