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Mirrors > Home > MPE Home > Th. List > hashle2pr | Structured version Visualization version GIF version |
Description: A nonempty set of size less than or equal to two is an unordered pair of sets. (Contributed by AV, 24-Nov-2021.) |
Ref | Expression |
---|---|
hashle2pr | ⊢ ((𝑃 ∈ 𝑉 ∧ 𝑃 ≠ ∅) → ((♯‘𝑃) ≤ 2 ↔ ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | hashxnn0 14236 | . . . . . . 7 ⊢ (𝑃 ∈ 𝑉 → (♯‘𝑃) ∈ ℕ0*) | |
2 | xnn0le2is012 13162 | . . . . . . 7 ⊢ (((♯‘𝑃) ∈ ℕ0* ∧ (♯‘𝑃) ≤ 2) → ((♯‘𝑃) = 0 ∨ (♯‘𝑃) = 1 ∨ (♯‘𝑃) = 2)) | |
3 | 1, 2 | sylan 580 | . . . . . 6 ⊢ ((𝑃 ∈ 𝑉 ∧ (♯‘𝑃) ≤ 2) → ((♯‘𝑃) = 0 ∨ (♯‘𝑃) = 1 ∨ (♯‘𝑃) = 2)) |
4 | 3 | ex 413 | . . . . 5 ⊢ (𝑃 ∈ 𝑉 → ((♯‘𝑃) ≤ 2 → ((♯‘𝑃) = 0 ∨ (♯‘𝑃) = 1 ∨ (♯‘𝑃) = 2))) |
5 | hasheq0 14260 | . . . . . . . . 9 ⊢ (𝑃 ∈ 𝑉 → ((♯‘𝑃) = 0 ↔ 𝑃 = ∅)) | |
6 | eqneqall 2953 | . . . . . . . . 9 ⊢ (𝑃 = ∅ → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) | |
7 | 5, 6 | syl6bi 252 | . . . . . . . 8 ⊢ (𝑃 ∈ 𝑉 → ((♯‘𝑃) = 0 → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
8 | 7 | com12 32 | . . . . . . 7 ⊢ ((♯‘𝑃) = 0 → (𝑃 ∈ 𝑉 → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
9 | hash1snb 14316 | . . . . . . . . . . 11 ⊢ (𝑃 ∈ 𝑉 → ((♯‘𝑃) = 1 ↔ ∃𝑐 𝑃 = {𝑐})) | |
10 | vex 3448 | . . . . . . . . . . . . 13 ⊢ 𝑐 ∈ V | |
11 | preq12 4695 | . . . . . . . . . . . . . . 15 ⊢ ((𝑎 = 𝑐 ∧ 𝑏 = 𝑐) → {𝑎, 𝑏} = {𝑐, 𝑐}) | |
12 | dfsn2 4598 | . . . . . . . . . . . . . . 15 ⊢ {𝑐} = {𝑐, 𝑐} | |
13 | 11, 12 | eqtr4di 2794 | . . . . . . . . . . . . . 14 ⊢ ((𝑎 = 𝑐 ∧ 𝑏 = 𝑐) → {𝑎, 𝑏} = {𝑐}) |
14 | 13 | eqeq2d 2747 | . . . . . . . . . . . . 13 ⊢ ((𝑎 = 𝑐 ∧ 𝑏 = 𝑐) → (𝑃 = {𝑎, 𝑏} ↔ 𝑃 = {𝑐})) |
15 | 10, 10, 14 | spc2ev 3565 | . . . . . . . . . . . 12 ⊢ (𝑃 = {𝑐} → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}) |
16 | 15 | exlimiv 1933 | . . . . . . . . . . 11 ⊢ (∃𝑐 𝑃 = {𝑐} → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}) |
17 | 9, 16 | syl6bi 252 | . . . . . . . . . 10 ⊢ (𝑃 ∈ 𝑉 → ((♯‘𝑃) = 1 → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) |
18 | 17 | imp 407 | . . . . . . . . 9 ⊢ ((𝑃 ∈ 𝑉 ∧ (♯‘𝑃) = 1) → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}) |
19 | 18 | a1d 25 | . . . . . . . 8 ⊢ ((𝑃 ∈ 𝑉 ∧ (♯‘𝑃) = 1) → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) |
20 | 19 | expcom 414 | . . . . . . 7 ⊢ ((♯‘𝑃) = 1 → (𝑃 ∈ 𝑉 → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
21 | hash2pr 14365 | . . . . . . . . 9 ⊢ ((𝑃 ∈ 𝑉 ∧ (♯‘𝑃) = 2) → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}) | |
22 | 21 | a1d 25 | . . . . . . . 8 ⊢ ((𝑃 ∈ 𝑉 ∧ (♯‘𝑃) = 2) → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) |
23 | 22 | expcom 414 | . . . . . . 7 ⊢ ((♯‘𝑃) = 2 → (𝑃 ∈ 𝑉 → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
24 | 8, 20, 23 | 3jaoi 1427 | . . . . . 6 ⊢ (((♯‘𝑃) = 0 ∨ (♯‘𝑃) = 1 ∨ (♯‘𝑃) = 2) → (𝑃 ∈ 𝑉 → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
25 | 24 | com12 32 | . . . . 5 ⊢ (𝑃 ∈ 𝑉 → (((♯‘𝑃) = 0 ∨ (♯‘𝑃) = 1 ∨ (♯‘𝑃) = 2) → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
26 | 4, 25 | syld 47 | . . . 4 ⊢ (𝑃 ∈ 𝑉 → ((♯‘𝑃) ≤ 2 → (𝑃 ≠ ∅ → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
27 | 26 | com23 86 | . . 3 ⊢ (𝑃 ∈ 𝑉 → (𝑃 ≠ ∅ → ((♯‘𝑃) ≤ 2 → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏}))) |
28 | 27 | imp 407 | . 2 ⊢ ((𝑃 ∈ 𝑉 ∧ 𝑃 ≠ ∅) → ((♯‘𝑃) ≤ 2 → ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) |
29 | fveq2 6840 | . . . 4 ⊢ (𝑃 = {𝑎, 𝑏} → (♯‘𝑃) = (♯‘{𝑎, 𝑏})) | |
30 | hashprlei 14364 | . . . . 5 ⊢ ({𝑎, 𝑏} ∈ Fin ∧ (♯‘{𝑎, 𝑏}) ≤ 2) | |
31 | 30 | simpri 486 | . . . 4 ⊢ (♯‘{𝑎, 𝑏}) ≤ 2 |
32 | 29, 31 | eqbrtrdi 5143 | . . 3 ⊢ (𝑃 = {𝑎, 𝑏} → (♯‘𝑃) ≤ 2) |
33 | 32 | exlimivv 1935 | . 2 ⊢ (∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏} → (♯‘𝑃) ≤ 2) |
34 | 28, 33 | impbid1 224 | 1 ⊢ ((𝑃 ∈ 𝑉 ∧ 𝑃 ≠ ∅) → ((♯‘𝑃) ≤ 2 ↔ ∃𝑎∃𝑏 𝑃 = {𝑎, 𝑏})) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 205 ∧ wa 396 ∨ w3o 1086 = wceq 1541 ∃wex 1781 ∈ wcel 2106 ≠ wne 2942 ∅c0 4281 {csn 4585 {cpr 4587 class class class wbr 5104 ‘cfv 6494 Fincfn 8880 0cc0 11048 1c1 11049 ≤ cle 11187 2c2 12205 ℕ0*cxnn0 12482 ♯chash 14227 |
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 1913 ax-6 1971 ax-7 2011 ax-8 2108 ax-9 2116 ax-10 2137 ax-11 2154 ax-12 2171 ax-ext 2707 ax-sep 5255 ax-nul 5262 ax-pow 5319 ax-pr 5383 ax-un 7669 ax-cnex 11104 ax-resscn 11105 ax-1cn 11106 ax-icn 11107 ax-addcl 11108 ax-addrcl 11109 ax-mulcl 11110 ax-mulrcl 11111 ax-mulcom 11112 ax-addass 11113 ax-mulass 11114 ax-distr 11115 ax-i2m1 11116 ax-1ne0 11117 ax-1rid 11118 ax-rnegex 11119 ax-rrecex 11120 ax-cnre 11121 ax-pre-lttri 11122 ax-pre-lttrn 11123 ax-pre-ltadd 11124 ax-pre-mulgt0 11125 |
This theorem depends on definitions: df-bi 206 df-an 397 df-or 846 df-3or 1088 df-3an 1089 df-tru 1544 df-fal 1554 df-ex 1782 df-nf 1786 df-sb 2068 df-mo 2538 df-eu 2567 df-clab 2714 df-cleq 2728 df-clel 2814 df-nfc 2888 df-ne 2943 df-nel 3049 df-ral 3064 df-rex 3073 df-reu 3353 df-rab 3407 df-v 3446 df-sbc 3739 df-csb 3855 df-dif 3912 df-un 3914 df-in 3916 df-ss 3926 df-pss 3928 df-nul 4282 df-if 4486 df-pw 4561 df-sn 4586 df-pr 4588 df-op 4592 df-uni 4865 df-int 4907 df-iun 4955 df-br 5105 df-opab 5167 df-mpt 5188 df-tr 5222 df-id 5530 df-eprel 5536 df-po 5544 df-so 5545 df-fr 5587 df-we 5589 df-xp 5638 df-rel 5639 df-cnv 5640 df-co 5641 df-dm 5642 df-rn 5643 df-res 5644 df-ima 5645 df-pred 6252 df-ord 6319 df-on 6320 df-lim 6321 df-suc 6322 df-iota 6446 df-fun 6496 df-fn 6497 df-f 6498 df-f1 6499 df-fo 6500 df-f1o 6501 df-fv 6502 df-riota 7310 df-ov 7357 df-oprab 7358 df-mpo 7359 df-om 7800 df-1st 7918 df-2nd 7919 df-frecs 8209 df-wrecs 8240 df-recs 8314 df-rdg 8353 df-1o 8409 df-2o 8410 df-oadd 8413 df-er 8645 df-en 8881 df-dom 8882 df-sdom 8883 df-fin 8884 df-dju 9834 df-card 9872 df-pnf 11188 df-mnf 11189 df-xr 11190 df-ltxr 11191 df-le 11192 df-sub 11384 df-neg 11385 df-nn 12151 df-2 12213 df-n0 12411 df-xnn0 12483 df-z 12497 df-uz 12761 df-fz 13422 df-hash 14228 |
This theorem is referenced by: hashle2prv 14374 |
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