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Mirrors > Home > MPE Home > Th. List > hash2exprb | Structured version Visualization version GIF version |
Description: A set of size two is an unordered pair if and only if it contains two different elements. (Contributed by Alexander van der Vekens, 14-Jan-2018.) |
Ref | Expression |
---|---|
hash2exprb | ⊢ (𝑉 ∈ 𝑊 → ((♯‘𝑉) = 2 ↔ ∃𝑎∃𝑏(𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏}))) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | hash2prde 13922 | . . 3 ⊢ ((𝑉 ∈ 𝑊 ∧ (♯‘𝑉) = 2) → ∃𝑎∃𝑏(𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏})) | |
2 | 1 | ex 416 | . 2 ⊢ (𝑉 ∈ 𝑊 → ((♯‘𝑉) = 2 → ∃𝑎∃𝑏(𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏}))) |
3 | hashprg 13848 | . . . . . . . . 9 ⊢ ((𝑎 ∈ V ∧ 𝑏 ∈ V) → (𝑎 ≠ 𝑏 ↔ (♯‘{𝑎, 𝑏}) = 2)) | |
4 | 3 | el2v 3406 | . . . . . . . 8 ⊢ (𝑎 ≠ 𝑏 ↔ (♯‘{𝑎, 𝑏}) = 2) |
5 | 4 | a1i 11 | . . . . . . 7 ⊢ (𝑉 = {𝑎, 𝑏} → (𝑎 ≠ 𝑏 ↔ (♯‘{𝑎, 𝑏}) = 2)) |
6 | 5 | biimpd 232 | . . . . . 6 ⊢ (𝑉 = {𝑎, 𝑏} → (𝑎 ≠ 𝑏 → (♯‘{𝑎, 𝑏}) = 2)) |
7 | fveqeq2 6683 | . . . . . 6 ⊢ (𝑉 = {𝑎, 𝑏} → ((♯‘𝑉) = 2 ↔ (♯‘{𝑎, 𝑏}) = 2)) | |
8 | 6, 7 | sylibrd 262 | . . . . 5 ⊢ (𝑉 = {𝑎, 𝑏} → (𝑎 ≠ 𝑏 → (♯‘𝑉) = 2)) |
9 | 8 | impcom 411 | . . . 4 ⊢ ((𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏}) → (♯‘𝑉) = 2) |
10 | 9 | a1i 11 | . . 3 ⊢ (𝑉 ∈ 𝑊 → ((𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏}) → (♯‘𝑉) = 2)) |
11 | 10 | exlimdvv 1941 | . 2 ⊢ (𝑉 ∈ 𝑊 → (∃𝑎∃𝑏(𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏}) → (♯‘𝑉) = 2)) |
12 | 2, 11 | impbid 215 | 1 ⊢ (𝑉 ∈ 𝑊 → ((♯‘𝑉) = 2 ↔ ∃𝑎∃𝑏(𝑎 ≠ 𝑏 ∧ 𝑉 = {𝑎, 𝑏}))) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 209 ∧ wa 399 = wceq 1542 ∃wex 1786 ∈ wcel 2114 ≠ wne 2934 Vcvv 3398 {cpr 4518 ‘cfv 6339 2c2 11771 ♯chash 13782 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1802 ax-4 1816 ax-5 1917 ax-6 1975 ax-7 2020 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2162 ax-12 2179 ax-ext 2710 ax-sep 5167 ax-nul 5174 ax-pow 5232 ax-pr 5296 ax-un 7479 ax-cnex 10671 ax-resscn 10672 ax-1cn 10673 ax-icn 10674 ax-addcl 10675 ax-addrcl 10676 ax-mulcl 10677 ax-mulrcl 10678 ax-mulcom 10679 ax-addass 10680 ax-mulass 10681 ax-distr 10682 ax-i2m1 10683 ax-1ne0 10684 ax-1rid 10685 ax-rnegex 10686 ax-rrecex 10687 ax-cnre 10688 ax-pre-lttri 10689 ax-pre-lttrn 10690 ax-pre-ltadd 10691 ax-pre-mulgt0 10692 |
This theorem depends on definitions: df-bi 210 df-an 400 df-or 847 df-3or 1089 df-3an 1090 df-tru 1545 df-fal 1555 df-ex 1787 df-nf 1791 df-sb 2075 df-mo 2540 df-eu 2570 df-clab 2717 df-cleq 2730 df-clel 2811 df-nfc 2881 df-ne 2935 df-nel 3039 df-ral 3058 df-rex 3059 df-reu 3060 df-rab 3062 df-v 3400 df-sbc 3681 df-csb 3791 df-dif 3846 df-un 3848 df-in 3850 df-ss 3860 df-pss 3862 df-nul 4212 df-if 4415 df-pw 4490 df-sn 4517 df-pr 4519 df-tp 4521 df-op 4523 df-uni 4797 df-int 4837 df-iun 4883 df-br 5031 df-opab 5093 df-mpt 5111 df-tr 5137 df-id 5429 df-eprel 5434 df-po 5442 df-so 5443 df-fr 5483 df-we 5485 df-xp 5531 df-rel 5532 df-cnv 5533 df-co 5534 df-dm 5535 df-rn 5536 df-res 5537 df-ima 5538 df-pred 6129 df-ord 6175 df-on 6176 df-lim 6177 df-suc 6178 df-iota 6297 df-fun 6341 df-fn 6342 df-f 6343 df-f1 6344 df-fo 6345 df-f1o 6346 df-fv 6347 df-riota 7127 df-ov 7173 df-oprab 7174 df-mpo 7175 df-om 7600 df-1st 7714 df-2nd 7715 df-wrecs 7976 df-recs 8037 df-rdg 8075 df-1o 8131 df-2o 8132 df-oadd 8135 df-er 8320 df-en 8556 df-dom 8557 df-sdom 8558 df-fin 8559 df-dju 9403 df-card 9441 df-pnf 10755 df-mnf 10756 df-xr 10757 df-ltxr 10758 df-le 10759 df-sub 10950 df-neg 10951 df-nn 11717 df-2 11779 df-n0 11977 df-z 12063 df-uz 12325 df-fz 12982 df-hash 13783 |
This theorem is referenced by: hash2prb 13924 prprelb 44502 |
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