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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 12510 | . 2 ⊢ -𝑒-∞ = if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) | |
2 | mnfnepnf 10699 | . . 3 ⊢ -∞ ≠ +∞ | |
3 | ifnefalse 4481 | . . 3 ⊢ (-∞ ≠ +∞ → if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) = if(-∞ = -∞, +∞, --∞)) | |
4 | 2, 3 | ax-mp 5 | . 2 ⊢ if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) = if(-∞ = -∞, +∞, --∞) |
5 | eqid 2823 | . . 3 ⊢ -∞ = -∞ | |
6 | 5 | iftruei 4476 | . 2 ⊢ if(-∞ = -∞, +∞, --∞) = +∞ |
7 | 1, 4, 6 | 3eqtri 2850 | 1 ⊢ -𝑒-∞ = +∞ |
Colors of variables: wff setvar class |
Syntax hints: = wceq 1537 ≠ wne 3018 ifcif 4469 +∞cpnf 10674 -∞cmnf 10675 -cneg 10873 -𝑒cxne 12507 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2161 ax-12 2177 ax-ext 2795 ax-sep 5205 ax-pow 5268 ax-un 7463 ax-cnex 10595 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-clab 2802 df-cleq 2816 df-clel 2895 df-nfc 2965 df-ne 3019 df-rab 3149 df-v 3498 df-un 3943 df-in 3945 df-ss 3954 df-if 4470 df-pw 4543 df-sn 4570 df-pr 4572 df-uni 4841 df-pnf 10679 df-mnf 10680 df-xr 10681 df-xneg 12510 |
This theorem is referenced by: xnegcl 12609 xnegneg 12610 xltnegi 12612 xnegid 12634 xnegdi 12644 xsubge0 12657 xmulneg1 12665 xmulpnf1n 12674 xadddi2 12693 xrsdsreclblem 20593 xaddeq0 30479 xrge0npcan 30683 carsgclctunlem2 31579 supminfxr 41747 supminfxr2 41752 liminf0 42081 liminflbuz2 42103 liminfpnfuz 42104 |
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