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Theorem xrrebnd 12190

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 12148	. . 3 ⊢ (𝐴 ∈ ℝ → -∞ < 𝐴)
2		ltpnf 12145	. . 3 ⊢ (𝐴 ∈ ℝ → 𝐴 < +∞)
3	1, 2	jca 555	. 2 ⊢ (𝐴 ∈ ℝ → (-∞ < 𝐴 ∧ 𝐴 < +∞))
4		nltpnft 12186	. . . . . 6 ⊢ (𝐴 ∈ ℝ^* → (𝐴 = +∞ ↔ ¬ 𝐴 < +∞))
5		ngtmnft 12188	. . . . . 6 ⊢ (𝐴 ∈ ℝ^* → (𝐴 = -∞ ↔ ¬ -∞ < 𝐴))
6	4, 5	orbi12d 748	. . . . 5 ⊢ (𝐴 ∈ ℝ^* → ((𝐴 = +∞ ∨ 𝐴 = -∞) ↔ (¬ 𝐴 < +∞ ∨ ¬ -∞ < 𝐴)))
7		ianor 510	. . . . . 6 ⊢ (¬ (-∞ < 𝐴 ∧ 𝐴 < +∞) ↔ (¬ -∞ < 𝐴 ∨ ¬ 𝐴 < +∞))
8		orcom 401	. . . . . 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 343	. . 3 ⊢ (𝐴 ∈ ℝ^* → ((-∞ < 𝐴 ∧ 𝐴 < +∞) ↔ ¬ (𝐴 = +∞ ∨ 𝐴 = -∞)))
12		elxr 12141	. . . . 5 ⊢ (𝐴 ∈ ℝ^* ↔ (𝐴 ∈ ℝ ∨ 𝐴 = +∞ ∨ 𝐴 = -∞))
13		3orass 1075	. . . . . 6 ⊢ ((𝐴 ∈ ℝ ∨ 𝐴 = +∞ ∨ 𝐴 = -∞) ↔ (𝐴 ∈ ℝ ∨ (𝐴 = +∞ ∨ 𝐴 = -∞)))
14		orcom 401	. . . . . 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 391	. . 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 382 ∧ wa 383 ∨ w3o 1071 = wceq 1630 ∈ wcel 2137 class class class wbr 4802 ℝcr 10125 +∞cpnf 10261 -∞cmnf 10262 ℝ^*cxr 10263 < clt 10264

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1869 ax-4 1884 ax-5 1986 ax-6 2052 ax-7 2088 ax-8 2139 ax-9 2146 ax-10 2166 ax-11 2181 ax-12 2194 ax-13 2389 ax-ext 2738 ax-sep 4931 ax-nul 4939 ax-pow 4990 ax-pr 5053 ax-un 7112 ax-cnex 10182 ax-resscn 10183 ax-pre-lttri 10200 ax-pre-lttrn 10201

This theorem depends on definitions: df-bi 197 df-or 384 df-an 385 df-3or 1073 df-3an 1074 df-tru 1633 df-ex 1852 df-nf 1857 df-sb 2045 df-eu 2609 df-mo 2610 df-clab 2745 df-cleq 2751 df-clel 2754 df-nfc 2889 df-ne 2931 df-nel 3034 df-ral 3053 df-rex 3054 df-rab 3057 df-v 3340 df-sbc 3575 df-csb 3673 df-dif 3716 df-un 3718 df-in 3720 df-ss 3727 df-nul 4057 df-if 4229 df-pw 4302 df-sn 4320 df-pr 4322 df-op 4326 df-uni 4587 df-br 4803 df-opab 4863 df-mpt 4880 df-id 5172 df-po 5185 df-so 5186 df-xp 5270 df-rel 5271 df-cnv 5272 df-co 5273 df-dm 5274 df-rn 5275 df-res 5276 df-ima 5277 df-iota 6010 df-fun 6049 df-fn 6050 df-f 6051 df-f1 6052 df-fo 6053 df-f1o 6054 df-fv 6055 df-er 7909 df-en 8120 df-dom 8121 df-sdom 8122 df-pnf 10266 df-mnf 10267 df-xr 10268 df-ltxr 10269 df-le 10270

This theorem is referenced by: xrre 12191 xrre2 12192 xrre3 12193 supxrre1 12351 elioc2 12427 elico2 12428 elicc2 12429 xblpnfps 22399 xblpnf 22400 isnghm3 22728 ovoliun 23471 ovolicopnf 23490 voliunlem3 23518 volsup 23522 itg2seq 23706 nmblore 27948 nmopre 29036 supxrgere 40045 supxrgelem 40049 supxrge 40050 suplesup 40051 infrpge 40063 limsupre 40374

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