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Theorem nnarcl 7681
 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 7617 . . . 4 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → 𝐴 ⊆ (𝐴 +𝑜 𝐵))
2 eloni 5721 . . . . . . 7 (𝐴 ∈ On → Ord 𝐴)
3 ordom 7059 . . . . . . 7 Ord ω
4 ordtr2 5756 . . . . . . 7 ((Ord 𝐴 ∧ Ord ω) → ((𝐴 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐴 ∈ ω))
52, 3, 4sylancl 693 . . . . . 6 (𝐴 ∈ On → ((𝐴 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐴 ∈ ω))
65expd 452 . . . . 5 (𝐴 ∈ On → (𝐴 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω)))
76adantr 481 . . . 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 7618 . . . . 5 ((𝐵 ∈ On ∧ 𝐴 ∈ On) → 𝐵 ⊆ (𝐴 +𝑜 𝐵))
109ancoms 469 . . . 4 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → 𝐵 ⊆ (𝐴 +𝑜 𝐵))
11 eloni 5721 . . . . . . 7 (𝐵 ∈ On → Ord 𝐵)
12 ordtr2 5756 . . . . . . 7 ((Ord 𝐵 ∧ Ord ω) → ((𝐵 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐵 ∈ ω))
1311, 3, 12sylancl 693 . . . . . 6 (𝐵 ∈ On → ((𝐵 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐵 ∈ ω))
1413expd 452 . . . . 5 (𝐵 ∈ On → (𝐵 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω)))
1514adantl 482 . . . 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 555 . 2 ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → (𝐴 ∈ ω ∧ 𝐵 ∈ ω)))
18 nnacl 7676 . 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 384   ∈ wcel 1988   ⊆ wss 3567  Ord word 5710  Oncon0 5711  (class class class)co 6635  ωcom 7050   +𝑜 coa 7542 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1720  ax-4 1735  ax-5 1837  ax-6 1886  ax-7 1933  ax-8 1990  ax-9 1997  ax-10 2017  ax-11 2032  ax-12 2045  ax-13 2244  ax-ext 2600  ax-rep 4762  ax-sep 4772  ax-nul 4780  ax-pow 4834  ax-pr 4897  ax-un 6934 This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3or 1037  df-3an 1038  df-tru 1484  df-ex 1703  df-nf 1708  df-sb 1879  df-eu 2472  df-mo 2473  df-clab 2607  df-cleq 2613  df-clel 2616  df-nfc 2751  df-ne 2792  df-ral 2914  df-rex 2915  df-reu 2916  df-rab 2918  df-v 3197  df-sbc 3430  df-csb 3527  df-dif 3570  df-un 3572  df-in 3574  df-ss 3581  df-pss 3583  df-nul 3908  df-if 4078  df-pw 4151  df-sn 4169  df-pr 4171  df-tp 4173  df-op 4175  df-uni 4428  df-iun 4513  df-br 4645  df-opab 4704  df-mpt 4721  df-tr 4744  df-id 5014  df-eprel 5019  df-po 5025  df-so 5026  df-fr 5063  df-we 5065  df-xp 5110  df-rel 5111  df-cnv 5112  df-co 5113  df-dm 5114  df-rn 5115  df-res 5116  df-ima 5117  df-pred 5668  df-ord 5714  df-on 5715  df-lim 5716  df-suc 5717  df-iota 5839  df-fun 5878  df-fn 5879  df-f 5880  df-f1 5881  df-fo 5882  df-f1o 5883  df-fv 5884  df-ov 6638  df-oprab 6639  df-mpt2 6640  df-om 7051  df-wrecs 7392  df-recs 7453  df-rdg 7491  df-oadd 7549 This theorem is referenced by:  finxpreclem4  33202
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