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Theorem nnmulcl 8010
 Description: Closure of multiplication of positive integers. (Contributed by NM, 12-Jan-1997.)
Assertion
Ref Expression
nnmulcl ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (𝐴 · 𝐵) ∈ ℕ)

Proof of Theorem nnmulcl
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 oveq2 5547 . . . . 5 (𝑥 = 1 → (𝐴 · 𝑥) = (𝐴 · 1))
21eleq1d 2122 . . . 4 (𝑥 = 1 → ((𝐴 · 𝑥) ∈ ℕ ↔ (𝐴 · 1) ∈ ℕ))
32imbi2d 223 . . 3 (𝑥 = 1 → ((𝐴 ∈ ℕ → (𝐴 · 𝑥) ∈ ℕ) ↔ (𝐴 ∈ ℕ → (𝐴 · 1) ∈ ℕ)))
4 oveq2 5547 . . . . 5 (𝑥 = 𝑦 → (𝐴 · 𝑥) = (𝐴 · 𝑦))
54eleq1d 2122 . . . 4 (𝑥 = 𝑦 → ((𝐴 · 𝑥) ∈ ℕ ↔ (𝐴 · 𝑦) ∈ ℕ))
65imbi2d 223 . . 3 (𝑥 = 𝑦 → ((𝐴 ∈ ℕ → (𝐴 · 𝑥) ∈ ℕ) ↔ (𝐴 ∈ ℕ → (𝐴 · 𝑦) ∈ ℕ)))
7 oveq2 5547 . . . . 5 (𝑥 = (𝑦 + 1) → (𝐴 · 𝑥) = (𝐴 · (𝑦 + 1)))
87eleq1d 2122 . . . 4 (𝑥 = (𝑦 + 1) → ((𝐴 · 𝑥) ∈ ℕ ↔ (𝐴 · (𝑦 + 1)) ∈ ℕ))
98imbi2d 223 . . 3 (𝑥 = (𝑦 + 1) → ((𝐴 ∈ ℕ → (𝐴 · 𝑥) ∈ ℕ) ↔ (𝐴 ∈ ℕ → (𝐴 · (𝑦 + 1)) ∈ ℕ)))
10 oveq2 5547 . . . . 5 (𝑥 = 𝐵 → (𝐴 · 𝑥) = (𝐴 · 𝐵))
1110eleq1d 2122 . . . 4 (𝑥 = 𝐵 → ((𝐴 · 𝑥) ∈ ℕ ↔ (𝐴 · 𝐵) ∈ ℕ))
1211imbi2d 223 . . 3 (𝑥 = 𝐵 → ((𝐴 ∈ ℕ → (𝐴 · 𝑥) ∈ ℕ) ↔ (𝐴 ∈ ℕ → (𝐴 · 𝐵) ∈ ℕ)))
13 nncn 7997 . . . 4 (𝐴 ∈ ℕ → 𝐴 ∈ ℂ)
14 mulid1 7081 . . . . . 6 (𝐴 ∈ ℂ → (𝐴 · 1) = 𝐴)
1514eleq1d 2122 . . . . 5 (𝐴 ∈ ℂ → ((𝐴 · 1) ∈ ℕ ↔ 𝐴 ∈ ℕ))
1615biimprd 151 . . . 4 (𝐴 ∈ ℂ → (𝐴 ∈ ℕ → (𝐴 · 1) ∈ ℕ))
1713, 16mpcom 36 . . 3 (𝐴 ∈ ℕ → (𝐴 · 1) ∈ ℕ)
18 nnaddcl 8009 . . . . . . . 8 (((𝐴 · 𝑦) ∈ ℕ ∧ 𝐴 ∈ ℕ) → ((𝐴 · 𝑦) + 𝐴) ∈ ℕ)
1918ancoms 259 . . . . . . 7 ((𝐴 ∈ ℕ ∧ (𝐴 · 𝑦) ∈ ℕ) → ((𝐴 · 𝑦) + 𝐴) ∈ ℕ)
20 nncn 7997 . . . . . . . . 9 (𝑦 ∈ ℕ → 𝑦 ∈ ℂ)
21 ax-1cn 7034 . . . . . . . . . . 11 1 ∈ ℂ
22 adddi 7070 . . . . . . . . . . 11 ((𝐴 ∈ ℂ ∧ 𝑦 ∈ ℂ ∧ 1 ∈ ℂ) → (𝐴 · (𝑦 + 1)) = ((𝐴 · 𝑦) + (𝐴 · 1)))
2321, 22mp3an3 1232 . . . . . . . . . 10 ((𝐴 ∈ ℂ ∧ 𝑦 ∈ ℂ) → (𝐴 · (𝑦 + 1)) = ((𝐴 · 𝑦) + (𝐴 · 1)))
2414oveq2d 5555 . . . . . . . . . . 11 (𝐴 ∈ ℂ → ((𝐴 · 𝑦) + (𝐴 · 1)) = ((𝐴 · 𝑦) + 𝐴))
2524adantr 265 . . . . . . . . . 10 ((𝐴 ∈ ℂ ∧ 𝑦 ∈ ℂ) → ((𝐴 · 𝑦) + (𝐴 · 1)) = ((𝐴 · 𝑦) + 𝐴))
2623, 25eqtrd 2088 . . . . . . . . 9 ((𝐴 ∈ ℂ ∧ 𝑦 ∈ ℂ) → (𝐴 · (𝑦 + 1)) = ((𝐴 · 𝑦) + 𝐴))
2713, 20, 26syl2an 277 . . . . . . . 8 ((𝐴 ∈ ℕ ∧ 𝑦 ∈ ℕ) → (𝐴 · (𝑦 + 1)) = ((𝐴 · 𝑦) + 𝐴))
2827eleq1d 2122 . . . . . . 7 ((𝐴 ∈ ℕ ∧ 𝑦 ∈ ℕ) → ((𝐴 · (𝑦 + 1)) ∈ ℕ ↔ ((𝐴 · 𝑦) + 𝐴) ∈ ℕ))
2919, 28syl5ibr 149 . . . . . 6 ((𝐴 ∈ ℕ ∧ 𝑦 ∈ ℕ) → ((𝐴 ∈ ℕ ∧ (𝐴 · 𝑦) ∈ ℕ) → (𝐴 · (𝑦 + 1)) ∈ ℕ))
3029exp4b 353 . . . . 5 (𝐴 ∈ ℕ → (𝑦 ∈ ℕ → (𝐴 ∈ ℕ → ((𝐴 · 𝑦) ∈ ℕ → (𝐴 · (𝑦 + 1)) ∈ ℕ))))
3130pm2.43b 50 . . . 4 (𝑦 ∈ ℕ → (𝐴 ∈ ℕ → ((𝐴 · 𝑦) ∈ ℕ → (𝐴 · (𝑦 + 1)) ∈ ℕ)))
3231a2d 26 . . 3 (𝑦 ∈ ℕ → ((𝐴 ∈ ℕ → (𝐴 · 𝑦) ∈ ℕ) → (𝐴 ∈ ℕ → (𝐴 · (𝑦 + 1)) ∈ ℕ)))
333, 6, 9, 12, 17, 32nnind 8005 . 2 (𝐵 ∈ ℕ → (𝐴 ∈ ℕ → (𝐴 · 𝐵) ∈ ℕ))
3433impcom 120 1 ((𝐴 ∈ ℕ ∧ 𝐵 ∈ ℕ) → (𝐴 · 𝐵) ∈ ℕ)
 Colors of variables: wff set class Syntax hints:   → wi 4   ∧ wa 101   = wceq 1259   ∈ wcel 1409  (class class class)co 5539  ℂcc 6944  1c1 6947   + caddc 6949   · cmul 6951  ℕcn 7989 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-io 640  ax-5 1352  ax-7 1353  ax-gen 1354  ax-ie1 1398  ax-ie2 1399  ax-8 1411  ax-10 1412  ax-11 1413  ax-i12 1414  ax-bndl 1415  ax-4 1416  ax-17 1435  ax-i9 1439  ax-ial 1443  ax-i5r 1444  ax-ext 2038  ax-sep 3902  ax-cnex 7032  ax-resscn 7033  ax-1cn 7034  ax-1re 7035  ax-icn 7036  ax-addcl 7037  ax-addrcl 7038  ax-mulcl 7039  ax-mulcom 7042  ax-addass 7043  ax-mulass 7044  ax-distr 7045  ax-1rid 7048  ax-cnre 7052 This theorem depends on definitions:  df-bi 114  df-3an 898  df-tru 1262  df-nf 1366  df-sb 1662  df-clab 2043  df-cleq 2049  df-clel 2052  df-nfc 2183  df-ral 2328  df-rex 2329  df-rab 2332  df-v 2576  df-un 2949  df-in 2951  df-ss 2958  df-sn 3408  df-pr 3409  df-op 3411  df-uni 3608  df-int 3643  df-br 3792  df-iota 4894  df-fv 4937  df-ov 5542  df-inn 7990 This theorem is referenced by:  nnmulcli  8011  nndivtr  8030  nnmulcld  8037  nn0mulcl  8274  qaddcl  8666  qmulcl  8668  modqmulnn  9291  nnexpcl  9432  nnsqcl  9488  faccl  9602  facdiv  9605  faclbnd3  9610  bcrpcl  9620
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