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Mirrors > Home > MPE Home > Th. List > unfi2 | Structured version Visualization version GIF version |
Description: The union of two finite sets is finite. Part of Corollary 6K of [Enderton] p. 144. This version of unfi 8785 is useful only if we assume the Axiom of Infinity (see comments in fin2inf 8781). (Contributed by NM, 22-Oct-2004.) (Revised by Mario Carneiro, 27-Apr-2015.) |
Ref | Expression |
---|---|
unfi2 | ⊢ ((𝐴 ≺ ω ∧ 𝐵 ≺ ω) → (𝐴 ∪ 𝐵) ≺ ω) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | isfinite2 8776 | . . 3 ⊢ (𝐴 ≺ ω → 𝐴 ∈ Fin) | |
2 | isfinite2 8776 | . . 3 ⊢ (𝐵 ≺ ω → 𝐵 ∈ Fin) | |
3 | unfi 8785 | . . 3 ⊢ ((𝐴 ∈ Fin ∧ 𝐵 ∈ Fin) → (𝐴 ∪ 𝐵) ∈ Fin) | |
4 | 1, 2, 3 | syl2an 597 | . 2 ⊢ ((𝐴 ≺ ω ∧ 𝐵 ≺ ω) → (𝐴 ∪ 𝐵) ∈ Fin) |
5 | fin2inf 8781 | . . . 4 ⊢ (𝐴 ≺ ω → ω ∈ V) | |
6 | 5 | adantr 483 | . . 3 ⊢ ((𝐴 ≺ ω ∧ 𝐵 ≺ ω) → ω ∈ V) |
7 | isfiniteg 8778 | . . 3 ⊢ (ω ∈ V → ((𝐴 ∪ 𝐵) ∈ Fin ↔ (𝐴 ∪ 𝐵) ≺ ω)) | |
8 | 6, 7 | syl 17 | . 2 ⊢ ((𝐴 ≺ ω ∧ 𝐵 ≺ ω) → ((𝐴 ∪ 𝐵) ∈ Fin ↔ (𝐴 ∪ 𝐵) ≺ ω)) |
9 | 4, 8 | mpbid 234 | 1 ⊢ ((𝐴 ≺ ω ∧ 𝐵 ≺ ω) → (𝐴 ∪ 𝐵) ≺ ω) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 208 ∧ wa 398 ∈ wcel 2114 Vcvv 3494 ∪ cun 3934 class class class wbr 5066 ωcom 7580 ≺ csdm 8508 Fincfn 8509 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2161 ax-12 2177 ax-ext 2793 ax-sep 5203 ax-nul 5210 ax-pow 5266 ax-pr 5330 ax-un 7461 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-3or 1084 df-3an 1085 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-mo 2622 df-eu 2654 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-ne 3017 df-ral 3143 df-rex 3144 df-reu 3145 df-rab 3147 df-v 3496 df-sbc 3773 df-csb 3884 df-dif 3939 df-un 3941 df-in 3943 df-ss 3952 df-pss 3954 df-nul 4292 df-if 4468 df-pw 4541 df-sn 4568 df-pr 4570 df-tp 4572 df-op 4574 df-uni 4839 df-int 4877 df-iun 4921 df-br 5067 df-opab 5129 df-mpt 5147 df-tr 5173 df-id 5460 df-eprel 5465 df-po 5474 df-so 5475 df-fr 5514 df-we 5516 df-xp 5561 df-rel 5562 df-cnv 5563 df-co 5564 df-dm 5565 df-rn 5566 df-res 5567 df-ima 5568 df-pred 6148 df-ord 6194 df-on 6195 df-lim 6196 df-suc 6197 df-iota 6314 df-fun 6357 df-fn 6358 df-f 6359 df-f1 6360 df-fo 6361 df-f1o 6362 df-fv 6363 df-ov 7159 df-oprab 7160 df-mpo 7161 df-om 7581 df-wrecs 7947 df-recs 8008 df-rdg 8046 df-oadd 8106 df-er 8289 df-en 8510 df-dom 8511 df-sdom 8512 df-fin 8513 |
This theorem is referenced by: djufi 9612 cdainflem 9613 infunsdom1 9635 |
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