Theorem nnarcl 7936

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

Step	Hyp	Ref	Expression
1		oaword1 7872	. . . 4 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → 𝐴 ⊆ (𝐴 +𝑜 𝐵))
2		eloni 5951	. . . . . . 7 ⊢ (𝐴 ∈ On → Ord 𝐴)
3		ordom 7308	. . . . . . 7 ⊢ Ord ω
4		ordtr2 5985	. . . . . . 7 ⊢ ((Ord 𝐴 ∧ Ord ω) → ((𝐴 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐴 ∈ ω))
5	2, 3, 4	sylancl 581	. . . . . 6 ⊢ (𝐴 ∈ On → ((𝐴 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐴 ∈ ω))
6	5	expd 405	. . . . 5 ⊢ (𝐴 ∈ On → (𝐴 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω)))
7	6	adantr 473	. . . 4 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω)))
8	1, 7	mpd 15	. . 3 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐴 ∈ ω))
9		oaword2 7873	. . . . 5 ⊢ ((𝐵 ∈ On ∧ 𝐴 ∈ On) → 𝐵 ⊆ (𝐴 +𝑜 𝐵))
10	9	ancoms 451	. . . 4 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → 𝐵 ⊆ (𝐴 +𝑜 𝐵))
11		eloni 5951	. . . . . . 7 ⊢ (𝐵 ∈ On → Ord 𝐵)
12		ordtr2 5985	. . . . . . 7 ⊢ ((Ord 𝐵 ∧ Ord ω) → ((𝐵 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐵 ∈ ω))
13	11, 3, 12	sylancl 581	. . . . . 6 ⊢ (𝐵 ∈ On → ((𝐵 ⊆ (𝐴 +𝑜 𝐵) ∧ (𝐴 +𝑜 𝐵) ∈ ω) → 𝐵 ∈ ω))
14	13	expd 405	. . . . 5 ⊢ (𝐵 ∈ On → (𝐵 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω)))
15	14	adantl 474	. . . 4 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐵 ⊆ (𝐴 +𝑜 𝐵) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω)))
16	10, 15	mpd 15	. . 3 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → 𝐵 ∈ ω))
17	8, 16	jcad 509	. 2 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω → (𝐴 ∈ ω ∧ 𝐵 ∈ ω)))
18		nnacl 7931	. 2 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (𝐴 +𝑜 𝐵) ∈ ω)
19	17, 18	impbid1 217	1 ⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ((𝐴 +𝑜 𝐵) ∈ ω ↔ (𝐴 ∈ ω ∧ 𝐵 ∈ ω)))

Syntax hints:   → wi 4   ↔ wb 198   ∧ wa 385   ∈ wcel 2157   ⊆ wss 3769  Ord word 5940  Oncon0 5941  (class class class)co 6878  ωcom 7299   +_𝑜 coa 7796

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1891  ax-4 1905  ax-5 2006  ax-6 2072  ax-7 2107  ax-8 2159  ax-9 2166  ax-10 2185  ax-11 2200  ax-12 2213  ax-13 2377  ax-ext 2777  ax-rep 4964  ax-sep 4975  ax-nul 4983  ax-pow 5035  ax-pr 5097  ax-un 7183

This theorem depends on definitions:  df-bi 199  df-an 386  df-or 875  df-3or 1109  df-3an 1110  df-tru 1657  df-ex 1876  df-nf 1880  df-sb 2065  df-mo 2591  df-eu 2609  df-clab 2786  df-cleq 2792  df-clel 2795  df-nfc 2930  df-ne 2972  df-ral 3094  df-rex 3095  df-reu 3096  df-rab 3098  df-v 3387  df-sbc 3634  df-csb 3729  df-dif 3772  df-un 3774  df-in 3776  df-ss 3783  df-pss 3785  df-nul 4116  df-if 4278  df-pw 4351  df-sn 4369  df-pr 4371  df-tp 4373  df-op 4375  df-uni 4629  df-iun 4712  df-br 4844  df-opab 4906  df-mpt 4923  df-tr 4946  df-id 5220  df-eprel 5225  df-po 5233  df-so 5234  df-fr 5271  df-we 5273  df-xp 5318  df-rel 5319  df-cnv 5320  df-co 5321  df-dm 5322  df-rn 5323  df-res 5324  df-ima 5325  df-pred 5898  df-ord 5944  df-on 5945  df-lim 5946  df-suc 5947  df-iota 6064  df-fun 6103  df-fn 6104  df-f 6105  df-f1 6106  df-fo 6107  df-f1o 6108  df-fv 6109  df-ov 6881  df-oprab 6882  df-mpt2 6883  df-om 7300  df-wrecs 7645  df-recs 7707  df-rdg 7745  df-oadd 7803

This theorem is referenced by:  finxpreclem4  33729