Description: Plus infinity belongs to the set of extended reals. (Contributed by NM, 13-Oct-2005) (Proof shortened by Anthony Hart, 29-Aug-2011)
Ref | Expression | ||
---|---|---|---|
Assertion | pnfxr | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssun2 | |
|
2 | pnfex | |
|
3 | 2 | prid1 | |
4 | 1 3 | sselii | |
5 | df-xr | |
|
6 | 4 5 | eleqtrri | |