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Mirrors > Home > MPE Home > Th. List > sgnmnf | Structured version Visualization version GIF version |
Description: The signum of -∞ is -1. (Contributed by David A. Wheeler, 26-Jun-2016.) |
Ref | Expression |
---|---|
sgnmnf | ⊢ (sgn‘-∞) = -1 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | mnfxr 11296 | . 2 ⊢ -∞ ∈ ℝ* | |
2 | mnflt0 13132 | . 2 ⊢ -∞ < 0 | |
3 | sgnn 15068 | . 2 ⊢ ((-∞ ∈ ℝ* ∧ -∞ < 0) → (sgn‘-∞) = -1) | |
4 | 1, 2, 3 | mp2an 691 | 1 ⊢ (sgn‘-∞) = -1 |
Colors of variables: wff setvar class |
Syntax hints: = wceq 1534 ∈ wcel 2099 class class class wbr 5143 ‘cfv 6543 0cc0 11133 1c1 11134 -∞cmnf 11271 ℝ*cxr 11272 < clt 11273 -cneg 11470 sgncsgn 15060 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1790 ax-4 1804 ax-5 1906 ax-6 1964 ax-7 2004 ax-8 2101 ax-9 2109 ax-10 2130 ax-11 2147 ax-12 2167 ax-ext 2699 ax-sep 5294 ax-nul 5301 ax-pow 5360 ax-pr 5424 ax-un 7735 ax-cnex 11189 ax-resscn 11190 ax-1cn 11191 ax-icn 11192 ax-addcl 11193 ax-addrcl 11194 ax-mulcl 11195 ax-i2m1 11201 ax-rnegex 11204 ax-cnre 11206 ax-pre-lttri 11207 ax-pre-lttrn 11208 |
This theorem depends on definitions: df-bi 206 df-an 396 df-or 847 df-3or 1086 df-3an 1087 df-tru 1537 df-fal 1547 df-ex 1775 df-nf 1779 df-sb 2061 df-mo 2530 df-eu 2559 df-clab 2706 df-cleq 2720 df-clel 2806 df-nfc 2881 df-ne 2937 df-nel 3043 df-ral 3058 df-rex 3067 df-rab 3429 df-v 3472 df-sbc 3776 df-csb 3891 df-dif 3948 df-un 3950 df-in 3952 df-ss 3962 df-nul 4320 df-if 4526 df-pw 4601 df-sn 4626 df-pr 4628 df-op 4632 df-uni 4905 df-br 5144 df-opab 5206 df-mpt 5227 df-id 5571 df-po 5585 df-so 5586 df-xp 5679 df-rel 5680 df-cnv 5681 df-co 5682 df-dm 5683 df-rn 5684 df-res 5685 df-ima 5686 df-iota 6495 df-fun 6545 df-fn 6546 df-f 6547 df-f1 6548 df-fo 6549 df-f1o 6550 df-fv 6551 df-ov 7418 df-er 8719 df-en 8959 df-dom 8960 df-sdom 8961 df-pnf 11275 df-mnf 11276 df-xr 11277 df-ltxr 11278 df-neg 11472 df-sgn 15061 |
This theorem is referenced by: (None) |
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