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Mirrors > Home > MPE Home > Th. List > infpss | Structured version Visualization version GIF version |
Description: Every infinite set has an equinumerous proper subset, proved without AC or Infinity. Exercise 7 of [TakeutiZaring] p. 91. See also infpssALT 10307. (Contributed by NM, 23-Oct-2004.) (Revised by Mario Carneiro, 30-Apr-2015.) |
Ref | Expression |
---|---|
infpss | ⊢ (ω ≼ 𝐴 → ∃𝑥(𝑥 ⊊ 𝐴 ∧ 𝑥 ≈ 𝐴)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | infn0 9306 | . . 3 ⊢ (ω ≼ 𝐴 → 𝐴 ≠ ∅) | |
2 | n0 4341 | . . 3 ⊢ (𝐴 ≠ ∅ ↔ ∃𝑦 𝑦 ∈ 𝐴) | |
3 | 1, 2 | sylib 217 | . 2 ⊢ (ω ≼ 𝐴 → ∃𝑦 𝑦 ∈ 𝐴) |
4 | reldom 8944 | . . . . . 6 ⊢ Rel ≼ | |
5 | 4 | brrelex2i 5726 | . . . . 5 ⊢ (ω ≼ 𝐴 → 𝐴 ∈ V) |
6 | 5 | difexd 5322 | . . . 4 ⊢ (ω ≼ 𝐴 → (𝐴 ∖ {𝑦}) ∈ V) |
7 | 6 | adantr 480 | . . 3 ⊢ ((ω ≼ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐴 ∖ {𝑦}) ∈ V) |
8 | simpr 484 | . . . . 5 ⊢ ((ω ≼ 𝐴 ∧ 𝑦 ∈ 𝐴) → 𝑦 ∈ 𝐴) | |
9 | difsnpss 4805 | . . . . 5 ⊢ (𝑦 ∈ 𝐴 ↔ (𝐴 ∖ {𝑦}) ⊊ 𝐴) | |
10 | 8, 9 | sylib 217 | . . . 4 ⊢ ((ω ≼ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐴 ∖ {𝑦}) ⊊ 𝐴) |
11 | infdifsn 9651 | . . . . 5 ⊢ (ω ≼ 𝐴 → (𝐴 ∖ {𝑦}) ≈ 𝐴) | |
12 | 11 | adantr 480 | . . . 4 ⊢ ((ω ≼ 𝐴 ∧ 𝑦 ∈ 𝐴) → (𝐴 ∖ {𝑦}) ≈ 𝐴) |
13 | 10, 12 | jca 511 | . . 3 ⊢ ((ω ≼ 𝐴 ∧ 𝑦 ∈ 𝐴) → ((𝐴 ∖ {𝑦}) ⊊ 𝐴 ∧ (𝐴 ∖ {𝑦}) ≈ 𝐴)) |
14 | psseq1 4082 | . . . 4 ⊢ (𝑥 = (𝐴 ∖ {𝑦}) → (𝑥 ⊊ 𝐴 ↔ (𝐴 ∖ {𝑦}) ⊊ 𝐴)) | |
15 | breq1 5144 | . . . 4 ⊢ (𝑥 = (𝐴 ∖ {𝑦}) → (𝑥 ≈ 𝐴 ↔ (𝐴 ∖ {𝑦}) ≈ 𝐴)) | |
16 | 14, 15 | anbi12d 630 | . . 3 ⊢ (𝑥 = (𝐴 ∖ {𝑦}) → ((𝑥 ⊊ 𝐴 ∧ 𝑥 ≈ 𝐴) ↔ ((𝐴 ∖ {𝑦}) ⊊ 𝐴 ∧ (𝐴 ∖ {𝑦}) ≈ 𝐴))) |
17 | 7, 13, 16 | spcedv 3582 | . 2 ⊢ ((ω ≼ 𝐴 ∧ 𝑦 ∈ 𝐴) → ∃𝑥(𝑥 ⊊ 𝐴 ∧ 𝑥 ≈ 𝐴)) |
18 | 3, 17 | exlimddv 1930 | 1 ⊢ (ω ≼ 𝐴 → ∃𝑥(𝑥 ⊊ 𝐴 ∧ 𝑥 ≈ 𝐴)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 395 = wceq 1533 ∃wex 1773 ∈ wcel 2098 ≠ wne 2934 Vcvv 3468 ∖ cdif 3940 ⊊ wpss 3944 ∅c0 4317 {csn 4623 class class class wbr 5141 ωcom 7851 ≈ cen 8935 ≼ cdom 8936 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1789 ax-4 1803 ax-5 1905 ax-6 1963 ax-7 2003 ax-8 2100 ax-9 2108 ax-10 2129 ax-11 2146 ax-12 2163 ax-ext 2697 ax-sep 5292 ax-nul 5299 ax-pow 5356 ax-pr 5420 ax-un 7721 |
This theorem depends on definitions: df-bi 206 df-an 396 df-or 845 df-3or 1085 df-3an 1086 df-tru 1536 df-fal 1546 df-ex 1774 df-nf 1778 df-sb 2060 df-mo 2528 df-eu 2557 df-clab 2704 df-cleq 2718 df-clel 2804 df-nfc 2879 df-ne 2935 df-ral 3056 df-rex 3065 df-rab 3427 df-v 3470 df-sbc 3773 df-csb 3889 df-dif 3946 df-un 3948 df-in 3950 df-ss 3960 df-pss 3962 df-nul 4318 df-if 4524 df-pw 4599 df-sn 4624 df-pr 4626 df-op 4630 df-uni 4903 df-br 5142 df-opab 5204 df-mpt 5225 df-tr 5259 df-id 5567 df-eprel 5573 df-po 5581 df-so 5582 df-fr 5624 df-we 5626 df-xp 5675 df-rel 5676 df-cnv 5677 df-co 5678 df-dm 5679 df-rn 5680 df-res 5681 df-ima 5682 df-ord 6360 df-on 6361 df-lim 6362 df-suc 6363 df-iota 6488 df-fun 6538 df-fn 6539 df-f 6540 df-f1 6541 df-fo 6542 df-f1o 6543 df-fv 6544 df-om 7852 df-er 8702 df-en 8939 df-dom 8940 |
This theorem is referenced by: isfin4-2 10308 |
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