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Theorem xrrebnd 11942

Description: An extended real is real iff it is strictly bounded by infinities. (Contributed by NM, 2-Feb-2006.)

**Assertion**
Ref	Expression
xrrebnd	⊢ (𝐴 ∈ ℝ^* → (𝐴 ∈ ℝ ↔ (-∞ < 𝐴 ∧ 𝐴 < +∞)))

**Proof of Theorem xrrebnd**
Step	Hyp	Ref	Expression
1		mnflt 11901	. . 3 ⊢ (𝐴 ∈ ℝ → -∞ < 𝐴)
2		ltpnf 11898	. . 3 ⊢ (𝐴 ∈ ℝ → 𝐴 < +∞)
3	1, 2	jca 554	. 2 ⊢ (𝐴 ∈ ℝ → (-∞ < 𝐴 ∧ 𝐴 < +∞))
4		nltpnft 11939	. . . . . 6 ⊢ (𝐴 ∈ ℝ^* → (𝐴 = +∞ ↔ ¬ 𝐴 < +∞))
5		ngtmnft 11941	. . . . . 6 ⊢ (𝐴 ∈ ℝ^* → (𝐴 = -∞ ↔ ¬ -∞ < 𝐴))
6	4, 5	orbi12d 745	. . . . 5 ⊢ (𝐴 ∈ ℝ^* → ((𝐴 = +∞ ∨ 𝐴 = -∞) ↔ (¬ 𝐴 < +∞ ∨ ¬ -∞ < 𝐴)))
7		ianor 509	. . . . . 6 ⊢ (¬ (-∞ < 𝐴 ∧ 𝐴 < +∞) ↔ (¬ -∞ < 𝐴 ∨ ¬ 𝐴 < +∞))
8		orcom 402	. . . . . 6 ⊢ ((¬ -∞ < 𝐴 ∨ ¬ 𝐴 < +∞) ↔ (¬ 𝐴 < +∞ ∨ ¬ -∞ < 𝐴))
9	7, 8	bitr2i 265	. . . . 5 ⊢ ((¬ 𝐴 < +∞ ∨ ¬ -∞ < 𝐴) ↔ ¬ (-∞ < 𝐴 ∧ 𝐴 < +∞))
10	6, 9	syl6bb 276	. . . 4 ⊢ (𝐴 ∈ ℝ^* → ((𝐴 = +∞ ∨ 𝐴 = -∞) ↔ ¬ (-∞ < 𝐴 ∧ 𝐴 < +∞)))
11	10	con2bid 344	. . 3 ⊢ (𝐴 ∈ ℝ^* → ((-∞ < 𝐴 ∧ 𝐴 < +∞) ↔ ¬ (𝐴 = +∞ ∨ 𝐴 = -∞)))
12		elxr 11894	. . . . 5 ⊢ (𝐴 ∈ ℝ^* ↔ (𝐴 ∈ ℝ ∨ 𝐴 = +∞ ∨ 𝐴 = -∞))
13		3orass 1039	. . . . . 6 ⊢ ((𝐴 ∈ ℝ ∨ 𝐴 = +∞ ∨ 𝐴 = -∞) ↔ (𝐴 ∈ ℝ ∨ (𝐴 = +∞ ∨ 𝐴 = -∞)))
14		orcom 402	. . . . . 6 ⊢ ((𝐴 ∈ ℝ ∨ (𝐴 = +∞ ∨ 𝐴 = -∞)) ↔ ((𝐴 = +∞ ∨ 𝐴 = -∞) ∨ 𝐴 ∈ ℝ))
15	13, 14	bitri 264	. . . . 5 ⊢ ((𝐴 ∈ ℝ ∨ 𝐴 = +∞ ∨ 𝐴 = -∞) ↔ ((𝐴 = +∞ ∨ 𝐴 = -∞) ∨ 𝐴 ∈ ℝ))
16	12, 15	sylbb 209	. . . 4 ⊢ (𝐴 ∈ ℝ^* → ((𝐴 = +∞ ∨ 𝐴 = -∞) ∨ 𝐴 ∈ ℝ))
17	16	ord 392	. . 3 ⊢ (𝐴 ∈ ℝ^* → (¬ (𝐴 = +∞ ∨ 𝐴 = -∞) → 𝐴 ∈ ℝ))
18	11, 17	sylbid 230	. 2 ⊢ (𝐴 ∈ ℝ^* → ((-∞ < 𝐴 ∧ 𝐴 < +∞) → 𝐴 ∈ ℝ))
19	3, 18	impbid2 216	1 ⊢ (𝐴 ∈ ℝ^* → (𝐴 ∈ ℝ ↔ (-∞ < 𝐴 ∧ 𝐴 < +∞)))

Colors of variables: wff setvar class

Syntax hints: ¬ wn 3 → wi 4 ↔ wb 196 ∨ wo 383 ∧ wa 384 ∨ w3o 1035 = wceq 1480 ∈ wcel 1987 class class class wbr 4613 ℝcr 9879 +∞cpnf 10015 -∞cmnf 10016 ℝ^*cxr 10017 < clt 10018

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1719 ax-4 1734 ax-5 1836 ax-6 1885 ax-7 1932 ax-8 1989 ax-9 1996 ax-10 2016 ax-11 2031 ax-12 2044 ax-13 2245 ax-ext 2601 ax-sep 4741 ax-nul 4749 ax-pow 4803 ax-pr 4867 ax-un 6902 ax-cnex 9936 ax-resscn 9937 ax-pre-lttri 9954 ax-pre-lttrn 9955

This theorem depends on definitions: df-bi 197 df-or 385 df-an 386 df-3or 1037 df-3an 1038 df-tru 1483 df-ex 1702 df-nf 1707 df-sb 1878 df-eu 2473 df-mo 2474 df-clab 2608 df-cleq 2614 df-clel 2617 df-nfc 2750 df-ne 2791 df-nel 2894 df-ral 2912 df-rex 2913 df-rab 2916 df-v 3188 df-sbc 3418 df-csb 3515 df-dif 3558 df-un 3560 df-in 3562 df-ss 3569 df-nul 3892 df-if 4059 df-pw 4132 df-sn 4149 df-pr 4151 df-op 4155 df-uni 4403 df-br 4614 df-opab 4674 df-mpt 4675 df-id 4989 df-po 4995 df-so 4996 df-xp 5080 df-rel 5081 df-cnv 5082 df-co 5083 df-dm 5084 df-rn 5085 df-res 5086 df-ima 5087 df-iota 5810 df-fun 5849 df-fn 5850 df-f 5851 df-f1 5852 df-fo 5853 df-f1o 5854 df-fv 5855 df-er 7687 df-en 7900 df-dom 7901 df-sdom 7902 df-pnf 10020 df-mnf 10021 df-xr 10022 df-ltxr 10023 df-le 10024

This theorem is referenced by: xrre 11943 xrre2 11944 xrre3 11945 supxrre1 12103 elioc2 12178 elico2 12179 elicc2 12180 xblpnfps 22110 xblpnf 22111 isnghm3 22439 ovoliun 23180 ovolicopnf 23199 voliunlem3 23227 volsup 23231 itg2seq 23415 nmblore 27487 nmopre 28575 supxrgere 39010 supxrgelem 39014 supxrge 39015 suplesup 39016 infrpge 39028 limsupre 39274

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