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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 11822 | . 2 ⊢ -𝑒-∞ = if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) | |
2 | mnfnepnf 9974 | . . 3 ⊢ -∞ ≠ +∞ | |
3 | ifnefalse 4048 | . . 3 ⊢ (-∞ ≠ +∞ → if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) = if(-∞ = -∞, +∞, --∞)) | |
4 | 2, 3 | ax-mp 5 | . 2 ⊢ if(-∞ = +∞, -∞, if(-∞ = -∞, +∞, --∞)) = if(-∞ = -∞, +∞, --∞) |
5 | eqid 2610 | . . 3 ⊢ -∞ = -∞ | |
6 | 5 | iftruei 4043 | . 2 ⊢ if(-∞ = -∞, +∞, --∞) = +∞ |
7 | 1, 4, 6 | 3eqtri 2636 | 1 ⊢ -𝑒-∞ = +∞ |
Colors of variables: wff setvar class |
Syntax hints: = wceq 1475 ≠ wne 2780 ifcif 4036 +∞cpnf 9950 -∞cmnf 9951 -cneg 10146 -𝑒cxne 11819 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-8 1979 ax-9 1986 ax-10 2006 ax-11 2021 ax-12 2034 ax-13 2234 ax-ext 2590 ax-sep 4709 ax-pow 4769 ax-un 6847 ax-cnex 9871 |
This theorem depends on definitions: df-bi 196 df-or 384 df-an 385 df-tru 1478 df-ex 1696 df-nf 1701 df-sb 1868 df-clab 2597 df-cleq 2603 df-clel 2606 df-nfc 2740 df-ne 2782 df-nel 2783 df-rex 2902 df-rab 2905 df-v 3175 df-un 3545 df-in 3547 df-ss 3554 df-if 4037 df-pw 4110 df-sn 4126 df-pr 4128 df-uni 4373 df-pnf 9955 df-mnf 9956 df-xr 9957 df-xneg 11822 |
This theorem is referenced by: xnegcl 11918 xnegneg 11919 xltnegi 11921 xnegid 11943 xnegdi 11950 xsubge0 11963 xmulneg1 11971 xmulpnf1n 11980 xadddi2 11999 xrsdsreclblem 19611 xaddeq0 28907 xrge0npcan 29025 carsgclctunlem2 29708 |
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