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Theorem rexneg 13157

Description: Minus a real number. Remark [BourbakiTop1] p. IV.15. (Contributed by FL, 26-Dec-2011.) (Proof shortened by Mario Carneiro, 20-Aug-2015.)

**Assertion**
Ref	Expression
rexneg	⊢ (𝐴 ∈ ℝ → -_𝑒𝐴 = -𝐴)

**Proof of Theorem rexneg**
Step	Hyp	Ref	Expression
1		df-xneg 13057	. 2 ⊢ -_𝑒𝐴 = if(𝐴 = +∞, -∞, if(𝐴 = -∞, +∞, -𝐴))
2		renepnf 11187	. . . 4 ⊢ (𝐴 ∈ ℝ → 𝐴 ≠ +∞)
3		ifnefalse 4479	. . . 4 ⊢ (𝐴 ≠ +∞ → if(𝐴 = +∞, -∞, if(𝐴 = -∞, +∞, -𝐴)) = if(𝐴 = -∞, +∞, -𝐴))
4	2, 3	syl 17	. . 3 ⊢ (𝐴 ∈ ℝ → if(𝐴 = +∞, -∞, if(𝐴 = -∞, +∞, -𝐴)) = if(𝐴 = -∞, +∞, -𝐴))
5		renemnf 11188	. . . 4 ⊢ (𝐴 ∈ ℝ → 𝐴 ≠ -∞)
6		ifnefalse 4479	. . . 4 ⊢ (𝐴 ≠ -∞ → if(𝐴 = -∞, +∞, -𝐴) = -𝐴)
7	5, 6	syl 17	. . 3 ⊢ (𝐴 ∈ ℝ → if(𝐴 = -∞, +∞, -𝐴) = -𝐴)
8	4, 7	eqtrd 2772	. 2 ⊢ (𝐴 ∈ ℝ → if(𝐴 = +∞, -∞, if(𝐴 = -∞, +∞, -𝐴)) = -𝐴)
9	1, 8	eqtrid 2784	1 ⊢ (𝐴 ∈ ℝ → -_𝑒𝐴 = -𝐴)

Colors of variables: wff setvar class

Syntax hints: → wi 4 = wceq 1542 ∈ wcel 2114 ≠ wne 2933 ifcif 4467 ℝcr 11031 +∞cpnf 11170 -∞cmnf 11171 -cneg 11372 -_𝑒cxne 13054

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 1912 ax-6 1969 ax-7 2010 ax-8 2116 ax-9 2124 ax-10 2147 ax-11 2163 ax-12 2185 ax-ext 2709 ax-sep 5232 ax-nul 5242 ax-pow 5303 ax-pr 5371 ax-un 7683 ax-resscn 11089

This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-3an 1089 df-tru 1545 df-fal 1555 df-ex 1782 df-nf 1786 df-sb 2069 df-mo 2540 df-eu 2570 df-clab 2716 df-cleq 2729 df-clel 2812 df-nfc 2886 df-ne 2934 df-nel 3038 df-ral 3053 df-rex 3063 df-rab 3391 df-v 3432 df-sbc 3730 df-csb 3839 df-dif 3893 df-un 3895 df-in 3897 df-ss 3907 df-nul 4275 df-if 4468 df-pw 4544 df-sn 4569 df-pr 4571 df-op 4575 df-uni 4852 df-br 5087 df-opab 5149 df-mpt 5168 df-id 5520 df-xp 5631 df-rel 5632 df-cnv 5633 df-co 5634 df-dm 5635 df-rn 5636 df-res 5637 df-ima 5638 df-iota 6449 df-fun 6495 df-fn 6496 df-f 6497 df-f1 6498 df-fo 6499 df-f1o 6500 df-fv 6501 df-er 8637 df-en 8888 df-dom 8889 df-sdom 8890 df-pnf 11175 df-mnf 11176 df-xneg 13057

This theorem is referenced by: xneg0 13158 xnegcl 13159 xnegneg 13160 xltnegi 13162 rexsub 13179 xnegid 13184 xnegdi 13194 xpncan 13197 xnpcan 13198 xmulneg1 13215 xmulm1 13227 xadddi 13241 xlt2addrd 32850 xrsmulgzz 33087 rexnegd 45594 xnegrecl 45887

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