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Mirrors > Home > MPE Home > Th. List > en3 | Structured version Visualization version GIF version |
Description: A set equinumerous to ordinal 3 is a triple. (Contributed by Mario Carneiro, 5-Jan-2016.) |
Ref | Expression |
---|---|
en3 | ⊢ (𝐴 ≈ 3o → ∃𝑥∃𝑦∃𝑧 𝐴 = {𝑥, 𝑦, 𝑧}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 2onn 8365 | . 2 ⊢ 2o ∈ ω | |
2 | df-3o 8201 | . 2 ⊢ 3o = suc 2o | |
3 | en2 8907 | . 2 ⊢ ((𝐴 ∖ {𝑥}) ≈ 2o → ∃𝑦∃𝑧(𝐴 ∖ {𝑥}) = {𝑦, 𝑧}) | |
4 | tpass 4665 | . . . 4 ⊢ {𝑥, 𝑦, 𝑧} = ({𝑥} ∪ {𝑦, 𝑧}) | |
5 | 4 | enp1ilem 8905 | . . 3 ⊢ (𝑥 ∈ 𝐴 → ((𝐴 ∖ {𝑥}) = {𝑦, 𝑧} → 𝐴 = {𝑥, 𝑦, 𝑧})) |
6 | 5 | 2eximdv 1927 | . 2 ⊢ (𝑥 ∈ 𝐴 → (∃𝑦∃𝑧(𝐴 ∖ {𝑥}) = {𝑦, 𝑧} → ∃𝑦∃𝑧 𝐴 = {𝑥, 𝑦, 𝑧})) |
7 | 1, 2, 3, 6 | enp1i 8906 | 1 ⊢ (𝐴 ≈ 3o → ∃𝑥∃𝑦∃𝑧 𝐴 = {𝑥, 𝑦, 𝑧}) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 = wceq 1543 ∃wex 1787 ∈ wcel 2110 ∖ cdif 3860 {csn 4538 {cpr 4540 {ctp 4542 class class class wbr 5050 2oc2o 8193 3oc3o 8194 ≈ cen 8620 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1803 ax-4 1817 ax-5 1918 ax-6 1976 ax-7 2016 ax-8 2112 ax-9 2120 ax-10 2141 ax-11 2158 ax-12 2175 ax-ext 2708 ax-sep 5189 ax-nul 5196 ax-pow 5255 ax-pr 5319 ax-un 7520 |
This theorem depends on definitions: df-bi 210 df-an 400 df-or 848 df-3or 1090 df-3an 1091 df-tru 1546 df-fal 1556 df-ex 1788 df-nf 1792 df-sb 2071 df-mo 2539 df-eu 2568 df-clab 2715 df-cleq 2729 df-clel 2816 df-nfc 2886 df-ne 2940 df-ral 3063 df-rex 3064 df-reu 3065 df-rab 3067 df-v 3407 df-sbc 3692 df-csb 3809 df-dif 3866 df-un 3868 df-in 3870 df-ss 3880 df-pss 3882 df-nul 4235 df-if 4437 df-pw 4512 df-sn 4539 df-pr 4541 df-tp 4543 df-op 4545 df-uni 4817 df-br 5051 df-opab 5113 df-mpt 5133 df-tr 5159 df-id 5452 df-eprel 5457 df-po 5465 df-so 5466 df-fr 5506 df-we 5508 df-xp 5554 df-rel 5555 df-cnv 5556 df-co 5557 df-dm 5558 df-rn 5559 df-res 5560 df-ima 5561 df-ord 6213 df-on 6214 df-lim 6215 df-suc 6216 df-iota 6335 df-fun 6379 df-fn 6380 df-f 6381 df-f1 6382 df-fo 6383 df-f1o 6384 df-fv 6385 df-om 7642 df-1o 8199 df-2o 8200 df-3o 8201 df-er 8388 df-en 8624 |
This theorem is referenced by: en4 8909 hash3tr 14053 |
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