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| Description: If 𝐴 and 𝐵 are members of a Tarski class, their unordered pair is also an element of the class. JFM CLASSES2 th. 3 (partly). (Contributed by FL, 22-Feb-2011.) (Proof shortened by Mario Carneiro, 20-Jun-2013.) | 
| Ref | Expression | 
|---|---|
| tskpr | ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇 ∧ 𝐵 ∈ 𝑇) → {𝐴, 𝐵} ∈ 𝑇) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | simp1 1136 | . 2 ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇 ∧ 𝐵 ∈ 𝑇) → 𝑇 ∈ Tarski) | |
| 2 | prssi 4820 | . . 3 ⊢ ((𝐴 ∈ 𝑇 ∧ 𝐵 ∈ 𝑇) → {𝐴, 𝐵} ⊆ 𝑇) | |
| 3 | 2 | 3adant1 1130 | . 2 ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇 ∧ 𝐵 ∈ 𝑇) → {𝐴, 𝐵} ⊆ 𝑇) | 
| 4 | prfi 9364 | . . . . 5 ⊢ {𝐴, 𝐵} ∈ Fin | |
| 5 | isfinite 9693 | . . . . 5 ⊢ ({𝐴, 𝐵} ∈ Fin ↔ {𝐴, 𝐵} ≺ ω) | |
| 6 | 4, 5 | mpbi 230 | . . . 4 ⊢ {𝐴, 𝐵} ≺ ω | 
| 7 | ne0i 4340 | . . . . 5 ⊢ (𝐴 ∈ 𝑇 → 𝑇 ≠ ∅) | |
| 8 | tskinf 10810 | . . . . 5 ⊢ ((𝑇 ∈ Tarski ∧ 𝑇 ≠ ∅) → ω ≼ 𝑇) | |
| 9 | 7, 8 | sylan2 593 | . . . 4 ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇) → ω ≼ 𝑇) | 
| 10 | sdomdomtr 9151 | . . . 4 ⊢ (({𝐴, 𝐵} ≺ ω ∧ ω ≼ 𝑇) → {𝐴, 𝐵} ≺ 𝑇) | |
| 11 | 6, 9, 10 | sylancr 587 | . . 3 ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇) → {𝐴, 𝐵} ≺ 𝑇) | 
| 12 | 11 | 3adant3 1132 | . 2 ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇 ∧ 𝐵 ∈ 𝑇) → {𝐴, 𝐵} ≺ 𝑇) | 
| 13 | tskssel 10798 | . 2 ⊢ ((𝑇 ∈ Tarski ∧ {𝐴, 𝐵} ⊆ 𝑇 ∧ {𝐴, 𝐵} ≺ 𝑇) → {𝐴, 𝐵} ∈ 𝑇) | |
| 14 | 1, 3, 12, 13 | syl3anc 1372 | 1 ⊢ ((𝑇 ∈ Tarski ∧ 𝐴 ∈ 𝑇 ∧ 𝐵 ∈ 𝑇) → {𝐴, 𝐵} ∈ 𝑇) | 
| Colors of variables: wff setvar class | 
| Syntax hints: → wi 4 ∧ wa 395 ∧ w3a 1086 ∈ wcel 2107 ≠ wne 2939 ⊆ wss 3950 ∅c0 4332 {cpr 4627 class class class wbr 5142 ωcom 7888 ≼ cdom 8984 ≺ csdm 8985 Fincfn 8986 Tarskictsk 10789 | 
| This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1794 ax-4 1808 ax-5 1909 ax-6 1966 ax-7 2006 ax-8 2109 ax-9 2117 ax-10 2140 ax-11 2156 ax-12 2176 ax-ext 2707 ax-rep 5278 ax-sep 5295 ax-nul 5305 ax-pow 5364 ax-pr 5431 ax-un 7756 ax-inf2 9682 | 
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 848 df-3or 1087 df-3an 1088 df-tru 1542 df-fal 1552 df-ex 1779 df-nf 1783 df-sb 2064 df-mo 2539 df-eu 2568 df-clab 2714 df-cleq 2728 df-clel 2815 df-nfc 2891 df-ne 2940 df-ral 3061 df-rex 3070 df-reu 3380 df-rab 3436 df-v 3481 df-sbc 3788 df-csb 3899 df-dif 3953 df-un 3955 df-in 3957 df-ss 3967 df-pss 3970 df-nul 4333 df-if 4525 df-pw 4601 df-sn 4626 df-pr 4628 df-op 4632 df-uni 4907 df-int 4946 df-iun 4992 df-br 5143 df-opab 5205 df-mpt 5225 df-tr 5259 df-id 5577 df-eprel 5583 df-po 5591 df-so 5592 df-fr 5636 df-we 5638 df-xp 5690 df-rel 5691 df-cnv 5692 df-co 5693 df-dm 5694 df-rn 5695 df-res 5696 df-ima 5697 df-pred 6320 df-ord 6386 df-on 6387 df-lim 6388 df-suc 6389 df-iota 6513 df-fun 6562 df-fn 6563 df-f 6564 df-f1 6565 df-fo 6566 df-f1o 6567 df-fv 6568 df-ov 7435 df-om 7889 df-2nd 8016 df-frecs 8307 df-wrecs 8338 df-recs 8412 df-rdg 8451 df-1o 8507 df-2o 8508 df-er 8746 df-en 8987 df-dom 8988 df-sdom 8989 df-fin 8990 df-r1 9805 df-tsk 10790 | 
| This theorem is referenced by: tskop 10812 tskwun 10825 tskun 10827 grutsk1 10862 | 
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