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Mirrors > Home > ILE Home > Th. List > mnfxr | GIF 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 | ⊢ -∞ ∈ ℝ* |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-mnf 7156 | . . . . 5 ⊢ -∞ = 𝒫 +∞ | |
2 | pnfex 8847 | . . . . . 6 ⊢ +∞ ∈ V | |
3 | 2 | pwex 3953 | . . . . 5 ⊢ 𝒫 +∞ ∈ V |
4 | 1, 3 | eqeltri 2151 | . . . 4 ⊢ -∞ ∈ V |
5 | 4 | prid2 3499 | . . 3 ⊢ -∞ ∈ {+∞, -∞} |
6 | elun2 3140 | . . 3 ⊢ (-∞ ∈ {+∞, -∞} → -∞ ∈ (ℝ ∪ {+∞, -∞})) | |
7 | 5, 6 | ax-mp 7 | . 2 ⊢ -∞ ∈ (ℝ ∪ {+∞, -∞}) |
8 | df-xr 7157 | . 2 ⊢ ℝ* = (ℝ ∪ {+∞, -∞}) | |
9 | 7, 8 | eleqtrri 2154 | 1 ⊢ -∞ ∈ ℝ* |
Colors of variables: wff set class |
Syntax hints: ∈ wcel 1433 Vcvv 2601 ∪ cun 2971 𝒫 cpw 3382 {cpr 3399 ℝcr 6980 +∞cpnf 7150 -∞cmnf 7151 ℝ*cxr 7152 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-io 662 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-10 1436 ax-11 1437 ax-i12 1438 ax-bndl 1439 ax-4 1440 ax-13 1444 ax-14 1445 ax-17 1459 ax-i9 1463 ax-ial 1467 ax-i5r 1468 ax-ext 2063 ax-sep 3896 ax-pow 3948 ax-un 4188 ax-cnex 7067 |
This theorem depends on definitions: df-bi 115 df-tru 1287 df-nf 1390 df-sb 1686 df-clab 2068 df-cleq 2074 df-clel 2077 df-nfc 2208 df-rex 2354 df-v 2603 df-un 2977 df-in 2979 df-ss 2986 df-pw 3384 df-sn 3404 df-pr 3405 df-uni 3602 df-pnf 7155 df-mnf 7156 df-xr 7157 |
This theorem is referenced by: elxr 8850 xrltnr 8855 mnflt 8858 mnfltpnf 8860 nltmnf 8863 mnfle 8867 xrltnsym 8868 xrlttri3 8872 ngtmnft 8885 xrrebnd 8886 xrre2 8888 xrre3 8889 ge0gtmnf 8890 xnegcl 8899 xltnegi 8902 xrex 8910 elioc2 8959 elico2 8960 elicc2 8961 ioomax 8971 iccmax 8972 elioomnf 8991 unirnioo 8996 |
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