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Theorem oacl 7899
 Description: Closure law for ordinal addition. Proposition 8.2 of [TakeutiZaring] p. 57. (Contributed by NM, 5-May-1995.)
Assertion
Ref Expression
oacl ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 +o 𝐵) ∈ On)

Proof of Theorem oacl
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 oveq2 6930 . . . 4 (𝑥 = ∅ → (𝐴 +o 𝑥) = (𝐴 +o ∅))
21eleq1d 2844 . . 3 (𝑥 = ∅ → ((𝐴 +o 𝑥) ∈ On ↔ (𝐴 +o ∅) ∈ On))
3 oveq2 6930 . . . 4 (𝑥 = 𝑦 → (𝐴 +o 𝑥) = (𝐴 +o 𝑦))
43eleq1d 2844 . . 3 (𝑥 = 𝑦 → ((𝐴 +o 𝑥) ∈ On ↔ (𝐴 +o 𝑦) ∈ On))
5 oveq2 6930 . . . 4 (𝑥 = suc 𝑦 → (𝐴 +o 𝑥) = (𝐴 +o suc 𝑦))
65eleq1d 2844 . . 3 (𝑥 = suc 𝑦 → ((𝐴 +o 𝑥) ∈ On ↔ (𝐴 +o suc 𝑦) ∈ On))
7 oveq2 6930 . . . 4 (𝑥 = 𝐵 → (𝐴 +o 𝑥) = (𝐴 +o 𝐵))
87eleq1d 2844 . . 3 (𝑥 = 𝐵 → ((𝐴 +o 𝑥) ∈ On ↔ (𝐴 +o 𝐵) ∈ On))
9 oa0 7880 . . . . 5 (𝐴 ∈ On → (𝐴 +o ∅) = 𝐴)
109eleq1d 2844 . . . 4 (𝐴 ∈ On → ((𝐴 +o ∅) ∈ On ↔ 𝐴 ∈ On))
1110ibir 260 . . 3 (𝐴 ∈ On → (𝐴 +o ∅) ∈ On)
12 suceloni 7291 . . . . 5 ((𝐴 +o 𝑦) ∈ On → suc (𝐴 +o 𝑦) ∈ On)
13 oasuc 7888 . . . . . 6 ((𝐴 ∈ On ∧ 𝑦 ∈ On) → (𝐴 +o suc 𝑦) = suc (𝐴 +o 𝑦))
1413eleq1d 2844 . . . . 5 ((𝐴 ∈ On ∧ 𝑦 ∈ On) → ((𝐴 +o suc 𝑦) ∈ On ↔ suc (𝐴 +o 𝑦) ∈ On))
1512, 14syl5ibr 238 . . . 4 ((𝐴 ∈ On ∧ 𝑦 ∈ On) → ((𝐴 +o 𝑦) ∈ On → (𝐴 +o suc 𝑦) ∈ On))
1615expcom 404 . . 3 (𝑦 ∈ On → (𝐴 ∈ On → ((𝐴 +o 𝑦) ∈ On → (𝐴 +o suc 𝑦) ∈ On)))
17 vex 3401 . . . . . 6 𝑥 ∈ V
18 iunon 7719 . . . . . 6 ((𝑥 ∈ V ∧ ∀𝑦𝑥 (𝐴 +o 𝑦) ∈ On) → 𝑦𝑥 (𝐴 +o 𝑦) ∈ On)
1917, 18mpan 680 . . . . 5 (∀𝑦𝑥 (𝐴 +o 𝑦) ∈ On → 𝑦𝑥 (𝐴 +o 𝑦) ∈ On)
20 oalim 7896 . . . . . . 7 ((𝐴 ∈ On ∧ (𝑥 ∈ V ∧ Lim 𝑥)) → (𝐴 +o 𝑥) = 𝑦𝑥 (𝐴 +o 𝑦))
2117, 20mpanr1 693 . . . . . 6 ((𝐴 ∈ On ∧ Lim 𝑥) → (𝐴 +o 𝑥) = 𝑦𝑥 (𝐴 +o 𝑦))
2221eleq1d 2844 . . . . 5 ((𝐴 ∈ On ∧ Lim 𝑥) → ((𝐴 +o 𝑥) ∈ On ↔ 𝑦𝑥 (𝐴 +o 𝑦) ∈ On))
2319, 22syl5ibr 238 . . . 4 ((𝐴 ∈ On ∧ Lim 𝑥) → (∀𝑦𝑥 (𝐴 +o 𝑦) ∈ On → (𝐴 +o 𝑥) ∈ On))
2423expcom 404 . . 3 (Lim 𝑥 → (𝐴 ∈ On → (∀𝑦𝑥 (𝐴 +o 𝑦) ∈ On → (𝐴 +o 𝑥) ∈ On)))
252, 4, 6, 8, 11, 16, 24tfinds3 7342 . 2 (𝐵 ∈ On → (𝐴 ∈ On → (𝐴 +o 𝐵) ∈ On))
2625impcom 398 1 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 +o 𝐵) ∈ On)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ∧ wa 386   = wceq 1601   ∈ wcel 2107  ∀wral 3090  Vcvv 3398  ∅c0 4141  ∪ ciun 4753  Oncon0 5976  Lim wlim 5977  suc csuc 5978  (class class class)co 6922   +o coa 7840 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1839  ax-4 1853  ax-5 1953  ax-6 2021  ax-7 2055  ax-8 2109  ax-9 2116  ax-10 2135  ax-11 2150  ax-12 2163  ax-13 2334  ax-ext 2754  ax-rep 5006  ax-sep 5017  ax-nul 5025  ax-pow 5077  ax-pr 5138  ax-un 7226 This theorem depends on definitions:  df-bi 199  df-an 387  df-or 837  df-3or 1072  df-3an 1073  df-tru 1605  df-ex 1824  df-nf 1828  df-sb 2012  df-mo 2551  df-eu 2587  df-clab 2764  df-cleq 2770  df-clel 2774  df-nfc 2921  df-ne 2970  df-ral 3095  df-rex 3096  df-reu 3097  df-rab 3099  df-v 3400  df-sbc 3653  df-csb 3752  df-dif 3795  df-un 3797  df-in 3799  df-ss 3806  df-pss 3808  df-nul 4142  df-if 4308  df-pw 4381  df-sn 4399  df-pr 4401  df-tp 4403  df-op 4405  df-uni 4672  df-iun 4755  df-br 4887  df-opab 4949  df-mpt 4966  df-tr 4988  df-id 5261  df-eprel 5266  df-po 5274  df-so 5275  df-fr 5314  df-we 5316  df-xp 5361  df-rel 5362  df-cnv 5363  df-co 5364  df-dm 5365  df-rn 5366  df-res 5367  df-ima 5368  df-pred 5933  df-ord 5979  df-on 5980  df-lim 5981  df-suc 5982  df-iota 6099  df-fun 6137  df-fn 6138  df-f 6139  df-f1 6140  df-fo 6141  df-f1o 6142  df-fv 6143  df-ov 6925  df-oprab 6926  df-mpt2 6927  df-om 7344  df-wrecs 7689  df-recs 7751  df-rdg 7789  df-oadd 7847 This theorem is referenced by:  omcl  7900  oaord  7911  oacan  7912  oaword  7913  oawordri  7914  oawordeulem  7918  oalimcl  7924  oaass  7925  oaf1o  7927  odi  7943  omopth2  7948  oeoalem  7960  oeoa  7961  oancom  8845  cantnfvalf  8859  dfac12lem2  9301  cdanum  9356  wunex3  9898  rdgeqoa  33813
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