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| Description: Membership in an old set. (Contributed by Scott Fenton, 7-Aug-2024.) | 
| Ref | Expression | 
|---|---|
| elold | ⊢ (𝐴 ∈ On → (𝑋 ∈ ( O ‘𝐴) ↔ ∃𝑏 ∈ 𝐴 𝑋 ∈ ( M ‘𝑏))) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | oldval 27893 | . . 3 ⊢ (𝐴 ∈ On → ( O ‘𝐴) = ∪ ( M “ 𝐴)) | |
| 2 | 1 | eleq2d 2827 | . 2 ⊢ (𝐴 ∈ On → (𝑋 ∈ ( O ‘𝐴) ↔ 𝑋 ∈ ∪ ( M “ 𝐴))) | 
| 3 | eluni 4910 | . . 3 ⊢ (𝑋 ∈ ∪ ( M “ 𝐴) ↔ ∃𝑦(𝑋 ∈ 𝑦 ∧ 𝑦 ∈ ( M “ 𝐴))) | |
| 4 | madef 27895 | . . . . . . . 8 ⊢ M :On⟶𝒫 No | |
| 5 | ffn 6736 | . . . . . . . 8 ⊢ ( M :On⟶𝒫 No → M Fn On) | |
| 6 | 4, 5 | ax-mp 5 | . . . . . . 7 ⊢ M Fn On | 
| 7 | onss 7805 | . . . . . . 7 ⊢ (𝐴 ∈ On → 𝐴 ⊆ On) | |
| 8 | fvelimab 6981 | . . . . . . 7 ⊢ (( M Fn On ∧ 𝐴 ⊆ On) → (𝑦 ∈ ( M “ 𝐴) ↔ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦)) | |
| 9 | 6, 7, 8 | sylancr 587 | . . . . . 6 ⊢ (𝐴 ∈ On → (𝑦 ∈ ( M “ 𝐴) ↔ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦)) | 
| 10 | 9 | anbi2d 630 | . . . . 5 ⊢ (𝐴 ∈ On → ((𝑋 ∈ 𝑦 ∧ 𝑦 ∈ ( M “ 𝐴)) ↔ (𝑋 ∈ 𝑦 ∧ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦))) | 
| 11 | 10 | exbidv 1921 | . . . 4 ⊢ (𝐴 ∈ On → (∃𝑦(𝑋 ∈ 𝑦 ∧ 𝑦 ∈ ( M “ 𝐴)) ↔ ∃𝑦(𝑋 ∈ 𝑦 ∧ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦))) | 
| 12 | fvex 6919 | . . . . . . 7 ⊢ ( M ‘𝑏) ∈ V | |
| 13 | 12 | clel3 3662 | . . . . . 6 ⊢ (𝑋 ∈ ( M ‘𝑏) ↔ ∃𝑦(𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦)) | 
| 14 | 13 | rexbii 3094 | . . . . 5 ⊢ (∃𝑏 ∈ 𝐴 𝑋 ∈ ( M ‘𝑏) ↔ ∃𝑏 ∈ 𝐴 ∃𝑦(𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦)) | 
| 15 | rexcom4 3288 | . . . . 5 ⊢ (∃𝑏 ∈ 𝐴 ∃𝑦(𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦) ↔ ∃𝑦∃𝑏 ∈ 𝐴 (𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦)) | |
| 16 | eqcom 2744 | . . . . . . . . 9 ⊢ (𝑦 = ( M ‘𝑏) ↔ ( M ‘𝑏) = 𝑦) | |
| 17 | 16 | anbi2ci 625 | . . . . . . . 8 ⊢ ((𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦) ↔ (𝑋 ∈ 𝑦 ∧ ( M ‘𝑏) = 𝑦)) | 
| 18 | 17 | rexbii 3094 | . . . . . . 7 ⊢ (∃𝑏 ∈ 𝐴 (𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦) ↔ ∃𝑏 ∈ 𝐴 (𝑋 ∈ 𝑦 ∧ ( M ‘𝑏) = 𝑦)) | 
| 19 | r19.42v 3191 | . . . . . . 7 ⊢ (∃𝑏 ∈ 𝐴 (𝑋 ∈ 𝑦 ∧ ( M ‘𝑏) = 𝑦) ↔ (𝑋 ∈ 𝑦 ∧ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦)) | |
| 20 | 18, 19 | bitri 275 | . . . . . 6 ⊢ (∃𝑏 ∈ 𝐴 (𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦) ↔ (𝑋 ∈ 𝑦 ∧ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦)) | 
| 21 | 20 | exbii 1848 | . . . . 5 ⊢ (∃𝑦∃𝑏 ∈ 𝐴 (𝑦 = ( M ‘𝑏) ∧ 𝑋 ∈ 𝑦) ↔ ∃𝑦(𝑋 ∈ 𝑦 ∧ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦)) | 
| 22 | 14, 15, 21 | 3bitrri 298 | . . . 4 ⊢ (∃𝑦(𝑋 ∈ 𝑦 ∧ ∃𝑏 ∈ 𝐴 ( M ‘𝑏) = 𝑦) ↔ ∃𝑏 ∈ 𝐴 𝑋 ∈ ( M ‘𝑏)) | 
| 23 | 11, 22 | bitrdi 287 | . . 3 ⊢ (𝐴 ∈ On → (∃𝑦(𝑋 ∈ 𝑦 ∧ 𝑦 ∈ ( M “ 𝐴)) ↔ ∃𝑏 ∈ 𝐴 𝑋 ∈ ( M ‘𝑏))) | 
| 24 | 3, 23 | bitrid 283 | . 2 ⊢ (𝐴 ∈ On → (𝑋 ∈ ∪ ( M “ 𝐴) ↔ ∃𝑏 ∈ 𝐴 𝑋 ∈ ( M ‘𝑏))) | 
| 25 | 2, 24 | bitrd 279 | 1 ⊢ (𝐴 ∈ On → (𝑋 ∈ ( O ‘𝐴) ↔ ∃𝑏 ∈ 𝐴 𝑋 ∈ ( M ‘𝑏))) | 
| Colors of variables: wff setvar class | 
| Syntax hints: → wi 4 ↔ wb 206 ∧ wa 395 = wceq 1540 ∃wex 1779 ∈ wcel 2108 ∃wrex 3070 ⊆ wss 3951 𝒫 cpw 4600 ∪ cuni 4907 “ cima 5688 Oncon0 6384 Fn wfn 6556 ⟶wf 6557 ‘cfv 6561 No csur 27684 M cmade 27881 O cold 27882 | 
| This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1795 ax-4 1809 ax-5 1910 ax-6 1967 ax-7 2007 ax-8 2110 ax-9 2118 ax-10 2141 ax-11 2157 ax-12 2177 ax-ext 2708 ax-rep 5279 ax-sep 5296 ax-nul 5306 ax-pow 5365 ax-pr 5432 ax-un 7755 | 
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-3or 1088 df-3an 1089 df-tru 1543 df-fal 1553 df-ex 1780 df-nf 1784 df-sb 2065 df-mo 2540 df-eu 2569 df-clab 2715 df-cleq 2729 df-clel 2816 df-nfc 2892 df-ne 2941 df-ral 3062 df-rex 3071 df-rmo 3380 df-reu 3381 df-rab 3437 df-v 3482 df-sbc 3789 df-csb 3900 df-dif 3954 df-un 3956 df-in 3958 df-ss 3968 df-pss 3971 df-nul 4334 df-if 4526 df-pw 4602 df-sn 4627 df-pr 4629 df-tp 4631 df-op 4633 df-uni 4908 df-int 4947 df-iun 4993 df-br 5144 df-opab 5206 df-mpt 5226 df-tr 5260 df-id 5578 df-eprel 5584 df-po 5592 df-so 5593 df-fr 5637 df-we 5639 df-xp 5691 df-rel 5692 df-cnv 5693 df-co 5694 df-dm 5695 df-rn 5696 df-res 5697 df-ima 5698 df-pred 6321 df-ord 6387 df-on 6388 df-suc 6390 df-iota 6514 df-fun 6563 df-fn 6564 df-f 6565 df-f1 6566 df-fo 6567 df-f1o 6568 df-fv 6569 df-riota 7388 df-ov 7434 df-oprab 7435 df-mpo 7436 df-2nd 8015 df-frecs 8306 df-wrecs 8337 df-recs 8411 df-1o 8506 df-2o 8507 df-no 27687 df-slt 27688 df-bday 27689 df-sslt 27826 df-scut 27828 df-made 27886 df-old 27887 | 
| This theorem is referenced by: oldssmade 27916 oldlim 27925 madebdayim 27926 oldbdayim 27927 madebdaylemold 27936 | 
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