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Theorem nnarcl 7854
Description: Reverse closure law for addition of natural numbers. Exercise 1 of [TakeutiZaring] p. 62 and its converse. (Contributed by NM, 12-Dec-2004.)
Assertion
Ref Expression
nnarcl ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω ↔ (𝐴 ∈ ω ∧ 𝐵 ∈ ω)))

Proof of Theorem nnarcl
StepHypRef Expression
1 oaword1 7790 . . . 4 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → 𝐴 ⊆ (𝐴 +𝑜 𝐵))
2 eloni 5875 . . . . . . 7 (𝐴 ∈ On → Ord 𝐴)
3 ordom 7225 . . . . . . 7 Ord ω
4 ordtr2 5910 . . . . . . 7 ((Ord 𝐴 ∧ Ord ω) → ((𝐴 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐴 ∈ ω))
52, 3, 4sylancl 574 . . . . . 6 (𝐴 ∈ On → ((𝐴 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐴 ∈ ω))
65expd 400 . . . . 5 (𝐴 ∈ On → (𝐴 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω)))
76adantr 466 . . . 4 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω)))
81, 7mpd 15 . . 3 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω))
9 oaword2 7791 . . . . 5 ((𝐵 ∈ On ∧ 𝐴 ∈ On) → 𝐵 ⊆ (𝐴 +𝑜 𝐵))
109ancoms 446 . . . 4 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → 𝐵 ⊆ (𝐴 +𝑜 𝐵))
11 eloni 5875 . . . . . . 7 (𝐵 ∈ On → Ord 𝐵)
12 ordtr2 5910 . . . . . . 7 ((Ord 𝐵 ∧ Ord ω) → ((𝐵 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐵 ∈ ω))
1311, 3, 12sylancl 574 . . . . . 6 (𝐵 ∈ On → ((𝐵 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐵 ∈ ω))
1413expd 400 . . . . 5 (𝐵 ∈ On → (𝐵 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω)))
1514adantl 467 . . . 4 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐵 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω)))
1610, 15mpd 15 . . 3 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω))
178, 16jcad 502 . 2 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → (𝐴 ∈ ω ∧ 𝐵 ∈ ω)))
18 nnacl 7849 . 2 ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (𝐴 +𝑜 𝐵) ∈ ω)
1917, 18impbid1 215 1 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω ↔ (𝐴 ∈ ω ∧ 𝐵 ∈ ω)))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 196  wa 382  wcel 2145  wss 3723  Ord word 5864  Oncon0 5865  (class class class)co 6796  ωcom 7216   +𝑜 coa 7714
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1870  ax-4 1885  ax-5 1991  ax-6 2057  ax-7 2093  ax-8 2147  ax-9 2154  ax-10 2174  ax-11 2190  ax-12 2203  ax-13 2408  ax-ext 2751  ax-rep 4905  ax-sep 4916  ax-nul 4924  ax-pow 4975  ax-pr 5035  ax-un 7100
This theorem depends on definitions:  df-bi 197  df-an 383  df-or 837  df-3or 1072  df-3an 1073  df-tru 1634  df-ex 1853  df-nf 1858  df-sb 2050  df-eu 2622  df-mo 2623  df-clab 2758  df-cleq 2764  df-clel 2767  df-nfc 2902  df-ne 2944  df-ral 3066  df-rex 3067  df-reu 3068  df-rab 3070  df-v 3353  df-sbc 3588  df-csb 3683  df-dif 3726  df-un 3728  df-in 3730  df-ss 3737  df-pss 3739  df-nul 4064  df-if 4227  df-pw 4300  df-sn 4318  df-pr 4320  df-tp 4322  df-op 4324  df-uni 4576  df-iun 4657  df-br 4788  df-opab 4848  df-mpt 4865  df-tr 4888  df-id 5158  df-eprel 5163  df-po 5171  df-so 5172  df-fr 5209  df-we 5211  df-xp 5256  df-rel 5257  df-cnv 5258  df-co 5259  df-dm 5260  df-rn 5261  df-res 5262  df-ima 5263  df-pred 5822  df-ord 5868  df-on 5869  df-lim 5870  df-suc 5871  df-iota 5993  df-fun 6032  df-fn 6033  df-f 6034  df-f1 6035  df-fo 6036  df-f1o 6037  df-fv 6038  df-ov 6799  df-oprab 6800  df-mpt2 6801  df-om 7217  df-wrecs 7563  df-recs 7625  df-rdg 7663  df-oadd 7721
This theorem is referenced by:  finxpreclem4  33568
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