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Theorem nnmcom 6232
Description: Multiplication of natural numbers is commutative. Theorem 4K(5) of [Enderton] p. 81. (Contributed by NM, 21-Sep-1995.) (Proof shortened by Andrew Salmon, 22-Oct-2011.)
Assertion
Ref Expression
nnmcom ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (𝐴 ·𝑜 𝐵) = (𝐵 ·𝑜 𝐴))

Proof of Theorem nnmcom
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 oveq1 5641 . . . . 5 (𝑥 = 𝐴 → (𝑥 ·𝑜 𝐵) = (𝐴 ·𝑜 𝐵))
2 oveq2 5642 . . . . 5 (𝑥 = 𝐴 → (𝐵 ·𝑜 𝑥) = (𝐵 ·𝑜 𝐴))
31, 2eqeq12d 2102 . . . 4 (𝑥 = 𝐴 → ((𝑥 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑥) ↔ (𝐴 ·𝑜 𝐵) = (𝐵 ·𝑜 𝐴)))
43imbi2d 228 . . 3 (𝑥 = 𝐴 → ((𝐵 ∈ ω → (𝑥 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑥)) ↔ (𝐵 ∈ ω → (𝐴 ·𝑜 𝐵) = (𝐵 ·𝑜 𝐴))))
5 oveq1 5641 . . . . 5 (𝑥 = ∅ → (𝑥 ·𝑜 𝐵) = (∅ ·𝑜 𝐵))
6 oveq2 5642 . . . . 5 (𝑥 = ∅ → (𝐵 ·𝑜 𝑥) = (𝐵 ·𝑜 ∅))
75, 6eqeq12d 2102 . . . 4 (𝑥 = ∅ → ((𝑥 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑥) ↔ (∅ ·𝑜 𝐵) = (𝐵 ·𝑜 ∅)))
8 oveq1 5641 . . . . 5 (𝑥 = 𝑦 → (𝑥 ·𝑜 𝐵) = (𝑦 ·𝑜 𝐵))
9 oveq2 5642 . . . . 5 (𝑥 = 𝑦 → (𝐵 ·𝑜 𝑥) = (𝐵 ·𝑜 𝑦))
108, 9eqeq12d 2102 . . . 4 (𝑥 = 𝑦 → ((𝑥 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑥) ↔ (𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑦)))
11 oveq1 5641 . . . . 5 (𝑥 = suc 𝑦 → (𝑥 ·𝑜 𝐵) = (suc 𝑦 ·𝑜 𝐵))
12 oveq2 5642 . . . . 5 (𝑥 = suc 𝑦 → (𝐵 ·𝑜 𝑥) = (𝐵 ·𝑜 suc 𝑦))
1311, 12eqeq12d 2102 . . . 4 (𝑥 = suc 𝑦 → ((𝑥 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑥) ↔ (suc 𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 suc 𝑦)))
14 nnm0r 6222 . . . . 5 (𝐵 ∈ ω → (∅ ·𝑜 𝐵) = ∅)
15 nnm0 6218 . . . . 5 (𝐵 ∈ ω → (𝐵 ·𝑜 ∅) = ∅)
1614, 15eqtr4d 2123 . . . 4 (𝐵 ∈ ω → (∅ ·𝑜 𝐵) = (𝐵 ·𝑜 ∅))
17 oveq1 5641 . . . . . 6 ((𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑦) → ((𝑦 ·𝑜 𝐵) +𝑜 𝐵) = ((𝐵 ·𝑜 𝑦) +𝑜 𝐵))
18 nnmsucr 6231 . . . . . . 7 ((𝑦 ∈ ω ∧ 𝐵 ∈ ω) → (suc 𝑦 ·𝑜 𝐵) = ((𝑦 ·𝑜 𝐵) +𝑜 𝐵))
19 nnmsuc 6220 . . . . . . . 8 ((𝐵 ∈ ω ∧ 𝑦 ∈ ω) → (𝐵 ·𝑜 suc 𝑦) = ((𝐵 ·𝑜 𝑦) +𝑜 𝐵))
2019ancoms 264 . . . . . . 7 ((𝑦 ∈ ω ∧ 𝐵 ∈ ω) → (𝐵 ·𝑜 suc 𝑦) = ((𝐵 ·𝑜 𝑦) +𝑜 𝐵))
2118, 20eqeq12d 2102 . . . . . 6 ((𝑦 ∈ ω ∧ 𝐵 ∈ ω) → ((suc 𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 suc 𝑦) ↔ ((𝑦 ·𝑜 𝐵) +𝑜 𝐵) = ((𝐵 ·𝑜 𝑦) +𝑜 𝐵)))
2217, 21syl5ibr 154 . . . . 5 ((𝑦 ∈ ω ∧ 𝐵 ∈ ω) → ((𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑦) → (suc 𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 suc 𝑦)))
2322ex 113 . . . 4 (𝑦 ∈ ω → (𝐵 ∈ ω → ((𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑦) → (suc 𝑦 ·𝑜 𝐵) = (𝐵 ·𝑜 suc 𝑦))))
247, 10, 13, 16, 23finds2 4406 . . 3 (𝑥 ∈ ω → (𝐵 ∈ ω → (𝑥 ·𝑜 𝐵) = (𝐵 ·𝑜 𝑥)))
254, 24vtoclga 2685 . 2 (𝐴 ∈ ω → (𝐵 ∈ ω → (𝐴 ·𝑜 𝐵) = (𝐵 ·𝑜 𝐴)))
2625imp 122 1 ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (𝐴 ·𝑜 𝐵) = (𝐵 ·𝑜 𝐴))
Colors of variables: wff set class
Syntax hints:  wi 4  wa 102   = wceq 1289  wcel 1438  c0 3284  suc csuc 4183  ωcom 4395  (class class class)co 5634   +𝑜 coa 6160   ·𝑜 comu 6161
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 579  ax-in2 580  ax-io 665  ax-5 1381  ax-7 1382  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-8 1440  ax-10 1441  ax-11 1442  ax-i12 1443  ax-bndl 1444  ax-4 1445  ax-13 1449  ax-14 1450  ax-17 1464  ax-i9 1468  ax-ial 1472  ax-i5r 1473  ax-ext 2070  ax-coll 3946  ax-sep 3949  ax-nul 3957  ax-pow 4001  ax-pr 4027  ax-un 4251  ax-setind 4343  ax-iinf 4393
This theorem depends on definitions:  df-bi 115  df-3an 926  df-tru 1292  df-fal 1295  df-nf 1395  df-sb 1693  df-eu 1951  df-mo 1952  df-clab 2075  df-cleq 2081  df-clel 2084  df-nfc 2217  df-ne 2256  df-ral 2364  df-rex 2365  df-reu 2366  df-rab 2368  df-v 2621  df-sbc 2839  df-csb 2932  df-dif 2999  df-un 3001  df-in 3003  df-ss 3010  df-nul 3285  df-pw 3427  df-sn 3447  df-pr 3448  df-op 3450  df-uni 3649  df-int 3684  df-iun 3727  df-br 3838  df-opab 3892  df-mpt 3893  df-tr 3929  df-id 4111  df-iord 4184  df-on 4186  df-suc 4189  df-iom 4396  df-xp 4434  df-rel 4435  df-cnv 4436  df-co 4437  df-dm 4438  df-rn 4439  df-res 4440  df-ima 4441  df-iota 4967  df-fun 5004  df-fn 5005  df-f 5006  df-f1 5007  df-fo 5008  df-f1o 5009  df-fv 5010  df-ov 5637  df-oprab 5638  df-mpt2 5639  df-1st 5893  df-2nd 5894  df-recs 6052  df-irdg 6117  df-oadd 6167  df-omul 6168
This theorem is referenced by:  nndir  6233  nn2m  6265  mulcompig  6869  enq0sym  6970  enq0ref  6971  enq0tr  6972  addcmpblnq0  6981  mulcmpblnq0  6982  mulcanenq0ec  6983  nnanq0  6996  distrnq0  6997  mulcomnq0  6998  addassnq0  7000  nq02m  7003
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