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Mirrors > Home > MPE Home > Th. List > xnegmnf | Structured version Visualization version GIF version |
Description: Minus -∞. Remark of [BourbakiTop1] p. IV.15. (Contributed by FL, 26-Dec-2011.) (Revised by Mario Carneiro, 20-Aug-2015.) |
Ref | Expression |
---|---|
xnegmnf | ⊢ -𝑒-∞ = +∞ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-xneg 12495 | . 2 ⊢ -𝑒-∞ = if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) | |
2 | mnfnepnf 10686 | . . 3 ⊢ -∞ ≠ +∞ | |
3 | ifnefalse 4437 | . . 3 ⊢ (-∞ ≠ +∞ → if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) = if(-∞ = -∞, +∞, --∞)) | |
4 | 2, 3 | ax-mp 5 | . 2 ⊢ if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) = if(-∞ = -∞, +∞, --∞) |
5 | eqid 2798 | . . 3 ⊢ -∞ = -∞ | |
6 | 5 | iftruei 4432 | . 2 ⊢ if(-∞ = -∞, +∞, --∞) = +∞ |
7 | 1, 4, 6 | 3eqtri 2825 | 1 ⊢ -𝑒-∞ = +∞ |
Colors of variables: wff setvar class |
Syntax hints: = wceq 1538 ≠ wne 2987 ifcif 4425 +∞cpnf 10661 -∞cmnf 10662 -cneg 10860 -𝑒cxne 12492 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1797 ax-4 1811 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2113 ax-9 2121 ax-10 2142 ax-11 2158 ax-12 2175 ax-ext 2770 ax-sep 5167 ax-pow 5231 ax-un 7441 ax-cnex 10582 |
This theorem depends on definitions: df-bi 210 df-an 400 df-or 845 df-tru 1541 df-ex 1782 df-nf 1786 df-sb 2070 df-clab 2777 df-cleq 2791 df-clel 2870 df-nfc 2938 df-ne 2988 df-rab 3115 df-v 3443 df-un 3886 df-in 3888 df-ss 3898 df-if 4426 df-pw 4499 df-sn 4526 df-pr 4528 df-uni 4801 df-pnf 10666 df-mnf 10667 df-xr 10668 df-xneg 12495 |
This theorem is referenced by: xnegcl 12594 xnegneg 12595 xltnegi 12597 xnegid 12619 xnegdi 12629 xsubge0 12642 xmulneg1 12650 xmulpnf1n 12659 xadddi2 12678 xrsdsreclblem 20137 xaddeq0 30503 xrge0npcan 30728 carsgclctunlem2 31687 supminfxr 42103 supminfxr2 42108 liminf0 42435 liminflbuz2 42457 liminfpnfuz 42458 |
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