Metamath Proof Explorer


Theorem fsumdvdsmul

Description: Product of two divisor sums. (This is also the main part of the proof that " sum_ k || N F ( k ) is a multiplicative function if F is".) (Contributed by Mario Carneiro, 2-Jul-2015) Avoid ax-mulf . (Revised by GG, 18-Apr-2025)

Ref Expression
Hypotheses mpodvdsmulf1o.1 ( 𝜑𝑀 ∈ ℕ )
mpodvdsmulf1o.2 ( 𝜑𝑁 ∈ ℕ )
mpodvdsmulf1o.3 ( 𝜑 → ( 𝑀 gcd 𝑁 ) = 1 )
mpodvdsmulf1o.x 𝑋 = { 𝑥 ∈ ℕ ∣ 𝑥𝑀 }
mpodvdsmulf1o.y 𝑌 = { 𝑥 ∈ ℕ ∣ 𝑥𝑁 }
mpodvdsmulf1o.z 𝑍 = { 𝑥 ∈ ℕ ∣ 𝑥 ∥ ( 𝑀 · 𝑁 ) }
fsumdvdsmul.4 ( ( 𝜑𝑗𝑋 ) → 𝐴 ∈ ℂ )
fsumdvdsmul.5 ( ( 𝜑𝑘𝑌 ) → 𝐵 ∈ ℂ )
fsumdvdsmul.6 ( ( 𝜑 ∧ ( 𝑗𝑋𝑘𝑌 ) ) → ( 𝐴 · 𝐵 ) = 𝐷 )
fsumdvdsmul.7 ( 𝑖 = ( 𝑗 · 𝑘 ) → 𝐶 = 𝐷 )
Assertion fsumdvdsmul ( 𝜑 → ( Σ 𝑗𝑋 𝐴 · Σ 𝑘𝑌 𝐵 ) = Σ 𝑖𝑍 𝐶 )

Proof

Step Hyp Ref Expression
1 mpodvdsmulf1o.1 ( 𝜑𝑀 ∈ ℕ )
2 mpodvdsmulf1o.2 ( 𝜑𝑁 ∈ ℕ )
3 mpodvdsmulf1o.3 ( 𝜑 → ( 𝑀 gcd 𝑁 ) = 1 )
4 mpodvdsmulf1o.x 𝑋 = { 𝑥 ∈ ℕ ∣ 𝑥𝑀 }
5 mpodvdsmulf1o.y 𝑌 = { 𝑥 ∈ ℕ ∣ 𝑥𝑁 }
6 mpodvdsmulf1o.z 𝑍 = { 𝑥 ∈ ℕ ∣ 𝑥 ∥ ( 𝑀 · 𝑁 ) }
7 fsumdvdsmul.4 ( ( 𝜑𝑗𝑋 ) → 𝐴 ∈ ℂ )
8 fsumdvdsmul.5 ( ( 𝜑𝑘𝑌 ) → 𝐵 ∈ ℂ )
9 fsumdvdsmul.6 ( ( 𝜑 ∧ ( 𝑗𝑋𝑘𝑌 ) ) → ( 𝐴 · 𝐵 ) = 𝐷 )
10 fsumdvdsmul.7 ( 𝑖 = ( 𝑗 · 𝑘 ) → 𝐶 = 𝐷 )
11 fzfid ( 𝜑 → ( 1 ... 𝑀 ) ∈ Fin )
12 dvdsssfz1 ( 𝑀 ∈ ℕ → { 𝑥 ∈ ℕ ∣ 𝑥𝑀 } ⊆ ( 1 ... 𝑀 ) )
13 1 12 syl ( 𝜑 → { 𝑥 ∈ ℕ ∣ 𝑥𝑀 } ⊆ ( 1 ... 𝑀 ) )
14 4 13 eqsstrid ( 𝜑𝑋 ⊆ ( 1 ... 𝑀 ) )
15 11 14 ssfid ( 𝜑𝑋 ∈ Fin )
16 fzfid ( 𝜑 → ( 1 ... 𝑁 ) ∈ Fin )
17 dvdsssfz1 ( 𝑁 ∈ ℕ → { 𝑥 ∈ ℕ ∣ 𝑥𝑁 } ⊆ ( 1 ... 𝑁 ) )
18 2 17 syl ( 𝜑 → { 𝑥 ∈ ℕ ∣ 𝑥𝑁 } ⊆ ( 1 ... 𝑁 ) )
19 5 18 eqsstrid ( 𝜑𝑌 ⊆ ( 1 ... 𝑁 ) )
20 16 19 ssfid ( 𝜑𝑌 ∈ Fin )
21 20 8 fsumcl ( 𝜑 → Σ 𝑘𝑌 𝐵 ∈ ℂ )
22 15 21 7 fsummulc1 ( 𝜑 → ( Σ 𝑗𝑋 𝐴 · Σ 𝑘𝑌 𝐵 ) = Σ 𝑗𝑋 ( 𝐴 · Σ 𝑘𝑌 𝐵 ) )
23 20 adantr ( ( 𝜑𝑗𝑋 ) → 𝑌 ∈ Fin )
24 8 adantlr ( ( ( 𝜑𝑗𝑋 ) ∧ 𝑘𝑌 ) → 𝐵 ∈ ℂ )
25 23 7 24 fsummulc2 ( ( 𝜑𝑗𝑋 ) → ( 𝐴 · Σ 𝑘𝑌 𝐵 ) = Σ 𝑘𝑌 ( 𝐴 · 𝐵 ) )
26 9 anassrs ( ( ( 𝜑𝑗𝑋 ) ∧ 𝑘𝑌 ) → ( 𝐴 · 𝐵 ) = 𝐷 )
27 26 sumeq2dv ( ( 𝜑𝑗𝑋 ) → Σ 𝑘𝑌 ( 𝐴 · 𝐵 ) = Σ 𝑘𝑌 𝐷 )
28 25 27 eqtrd ( ( 𝜑𝑗𝑋 ) → ( 𝐴 · Σ 𝑘𝑌 𝐵 ) = Σ 𝑘𝑌 𝐷 )
29 28 sumeq2dv ( 𝜑 → Σ 𝑗𝑋 ( 𝐴 · Σ 𝑘𝑌 𝐵 ) = Σ 𝑗𝑋 Σ 𝑘𝑌 𝐷 )
30 elxpi ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ∃ 𝑢𝑣 ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ ∧ ( 𝑢𝑋𝑣𝑌 ) ) )
31 fveq2 ( ⟨ 𝑢 , 𝑣 ⟩ = 𝑧 → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) )
32 31 eqcoms ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) )
33 fveq2 ( ⟨ 𝑢 , 𝑣 ⟩ = 𝑧 → ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( · ‘ 𝑧 ) )
34 33 eqcoms ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ → ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( · ‘ 𝑧 ) )
35 32 34 eqeq12d ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ → ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ ) ↔ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) = ( · ‘ 𝑧 ) ) )
36 35 biimpd ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ → ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) = ( · ‘ 𝑧 ) ) )
37 4 ssrab3 𝑋 ⊆ ℕ
38 nnsscn ℕ ⊆ ℂ
39 37 38 sstri 𝑋 ⊆ ℂ
40 39 sseli ( 𝑢𝑋𝑢 ∈ ℂ )
41 5 ssrab3 𝑌 ⊆ ℕ
42 41 38 sstri 𝑌 ⊆ ℂ
43 42 sseli ( 𝑣𝑌𝑣 ∈ ℂ )
44 ovmpot ( ( 𝑢 ∈ ℂ ∧ 𝑣 ∈ ℂ ) → ( 𝑢 ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) 𝑣 ) = ( 𝑢 · 𝑣 ) )
45 df-ov ( 𝑢 ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) 𝑣 ) = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ )
46 df-ov ( 𝑢 · 𝑣 ) = ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ )
47 44 45 46 3eqtr3g ( ( 𝑢 ∈ ℂ ∧ 𝑣 ∈ ℂ ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ ) )
48 40 43 47 syl2an ( ( 𝑢𝑋𝑣𝑌 ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ ⟨ 𝑢 , 𝑣 ⟩ ) = ( · ‘ ⟨ 𝑢 , 𝑣 ⟩ ) )
49 36 48 impel ( ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ ∧ ( 𝑢𝑋𝑣𝑌 ) ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) = ( · ‘ 𝑧 ) )
50 49 exlimivv ( ∃ 𝑢𝑣 ( 𝑧 = ⟨ 𝑢 , 𝑣 ⟩ ∧ ( 𝑢𝑋𝑣𝑌 ) ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) = ( · ‘ 𝑧 ) )
51 30 50 syl ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) = ( · ‘ 𝑧 ) )
52 51 eqcomd ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( · ‘ 𝑧 ) = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) )
53 52 csbeq1d ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( · ‘ 𝑧 ) / 𝑖 𝐶 = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 )
54 53 sumeq2i Σ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑧 ) / 𝑖 𝐶 = Σ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶
55 fveq2 ( 𝑧 = ⟨ 𝑗 , 𝑘 ⟩ → ( · ‘ 𝑧 ) = ( · ‘ ⟨ 𝑗 , 𝑘 ⟩ ) )
56 df-ov ( 𝑗 · 𝑘 ) = ( · ‘ ⟨ 𝑗 , 𝑘 ⟩ )
57 55 56 eqtr4di ( 𝑧 = ⟨ 𝑗 , 𝑘 ⟩ → ( · ‘ 𝑧 ) = ( 𝑗 · 𝑘 ) )
58 57 csbeq1d ( 𝑧 = ⟨ 𝑗 , 𝑘 ⟩ → ( · ‘ 𝑧 ) / 𝑖 𝐶 = ( 𝑗 · 𝑘 ) / 𝑖 𝐶 )
59 ovex ( 𝑗 · 𝑘 ) ∈ V
60 59 10 csbie ( 𝑗 · 𝑘 ) / 𝑖 𝐶 = 𝐷
61 58 60 eqtrdi ( 𝑧 = ⟨ 𝑗 , 𝑘 ⟩ → ( · ‘ 𝑧 ) / 𝑖 𝐶 = 𝐷 )
62 7 adantrr ( ( 𝜑 ∧ ( 𝑗𝑋𝑘𝑌 ) ) → 𝐴 ∈ ℂ )
63 8 adantrl ( ( 𝜑 ∧ ( 𝑗𝑋𝑘𝑌 ) ) → 𝐵 ∈ ℂ )
64 62 63 mulcld ( ( 𝜑 ∧ ( 𝑗𝑋𝑘𝑌 ) ) → ( 𝐴 · 𝐵 ) ∈ ℂ )
65 9 64 eqeltrrd ( ( 𝜑 ∧ ( 𝑗𝑋𝑘𝑌 ) ) → 𝐷 ∈ ℂ )
66 61 15 20 65 fsumxp ( 𝜑 → Σ 𝑗𝑋 Σ 𝑘𝑌 𝐷 = Σ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑧 ) / 𝑖 𝐶 )
67 nfcv 𝑤 𝐶
68 nfcsb1v 𝑖 𝑤 / 𝑖 𝐶
69 csbeq1a ( 𝑖 = 𝑤𝐶 = 𝑤 / 𝑖 𝐶 )
70 67 68 69 cbvsumi Σ 𝑖𝑍 𝐶 = Σ 𝑤𝑍 𝑤 / 𝑖 𝐶
71 csbeq1 ( 𝑤 = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) → 𝑤 / 𝑖 𝐶 = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 )
72 xpfi ( ( 𝑋 ∈ Fin ∧ 𝑌 ∈ Fin ) → ( 𝑋 × 𝑌 ) ∈ Fin )
73 15 20 72 syl2anc ( 𝜑 → ( 𝑋 × 𝑌 ) ∈ Fin )
74 1 2 3 4 5 6 mpodvdsmulf1o ( 𝜑 → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) : ( 𝑋 × 𝑌 ) –1-1-onto𝑍 )
75 fvres ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) ‘ 𝑧 ) = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) )
76 75 adantl ( ( 𝜑𝑧 ∈ ( 𝑋 × 𝑌 ) ) → ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) ‘ 𝑧 ) = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) )
77 65 ralrimivva ( 𝜑 → ∀ 𝑗𝑋𝑘𝑌 𝐷 ∈ ℂ )
78 61 eleq1d ( 𝑧 = ⟨ 𝑗 , 𝑘 ⟩ → ( ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ 𝐷 ∈ ℂ ) )
79 78 ralxp ( ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ∀ 𝑗𝑋𝑘𝑌 𝐷 ∈ ℂ )
80 77 79 sylibr ( 𝜑 → ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ )
81 fveq2 ( 𝑧 = 𝑤 → ( · ‘ 𝑧 ) = ( · ‘ 𝑤 ) )
82 81 csbeq1d ( 𝑧 = 𝑤 ( · ‘ 𝑧 ) / 𝑖 𝐶 = ( · ‘ 𝑤 ) / 𝑖 𝐶 )
83 82 eleq1d ( 𝑧 = 𝑤 → ( ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ ) )
84 83 cbvralvw ( ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ∀ 𝑤 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ )
85 id ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → 𝑧 ∈ ( 𝑋 × 𝑌 ) )
86 82 eqcoms ( 𝑤 = 𝑧 ( · ‘ 𝑧 ) / 𝑖 𝐶 = ( · ‘ 𝑤 ) / 𝑖 𝐶 )
87 86 adantl ( ( 𝑧 ∈ ( 𝑋 × 𝑌 ) ∧ 𝑤 = 𝑧 ) → ( · ‘ 𝑧 ) / 𝑖 𝐶 = ( · ‘ 𝑤 ) / 𝑖 𝐶 )
88 87 eleq1d ( ( 𝑧 ∈ ( 𝑋 × 𝑌 ) ∧ 𝑤 = 𝑧 ) → ( ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ ) )
89 53 eleq1d ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
90 89 adantr ( ( 𝑧 ∈ ( 𝑋 × 𝑌 ) ∧ 𝑤 = 𝑧 ) → ( ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
91 88 90 bitr3d ( ( 𝑧 ∈ ( 𝑋 × 𝑌 ) ∧ 𝑤 = 𝑧 ) → ( ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ ↔ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
92 85 91 rspcdv ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( ∀ 𝑤 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
93 92 com12 ( ∀ 𝑤 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ → ( 𝑧 ∈ ( 𝑋 × 𝑌 ) → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
94 93 ralrimiv ( ∀ 𝑤 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑤 ) / 𝑖 𝐶 ∈ ℂ → ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ )
95 84 94 sylbi ( ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( · ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ → ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ )
96 80 95 syl ( 𝜑 → ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ )
97 mpomulf ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) : ( ℂ × ℂ ) ⟶ ℂ
98 ffn ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) : ( ℂ × ℂ ) ⟶ ℂ → ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) Fn ( ℂ × ℂ ) )
99 97 98 ax-mp ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) Fn ( ℂ × ℂ )
100 xpss12 ( ( 𝑋 ⊆ ℂ ∧ 𝑌 ⊆ ℂ ) → ( 𝑋 × 𝑌 ) ⊆ ( ℂ × ℂ ) )
101 39 42 100 mp2an ( 𝑋 × 𝑌 ) ⊆ ( ℂ × ℂ )
102 71 eleq1d ( 𝑤 = ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) → ( 𝑤 / 𝑖 𝐶 ∈ ℂ ↔ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
103 102 ralima ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) Fn ( ℂ × ℂ ) ∧ ( 𝑋 × 𝑌 ) ⊆ ( ℂ × ℂ ) ) → ( ∀ 𝑤 ∈ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) “ ( 𝑋 × 𝑌 ) ) 𝑤 / 𝑖 𝐶 ∈ ℂ ↔ ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ) )
104 99 101 103 mp2an ( ∀ 𝑤 ∈ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) “ ( 𝑋 × 𝑌 ) ) 𝑤 / 𝑖 𝐶 ∈ ℂ ↔ ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ )
105 df-ima ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) “ ( 𝑋 × 𝑌 ) ) = ran ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) )
106 f1ofo ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) : ( 𝑋 × 𝑌 ) –1-1-onto𝑍 → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) : ( 𝑋 × 𝑌 ) –onto𝑍 )
107 forn ( ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) : ( 𝑋 × 𝑌 ) –onto𝑍 → ran ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) = 𝑍 )
108 74 106 107 3syl ( 𝜑 → ran ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ↾ ( 𝑋 × 𝑌 ) ) = 𝑍 )
109 105 108 eqtrid ( 𝜑 → ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) “ ( 𝑋 × 𝑌 ) ) = 𝑍 )
110 109 raleqdv ( 𝜑 → ( ∀ 𝑤 ∈ ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) “ ( 𝑋 × 𝑌 ) ) 𝑤 / 𝑖 𝐶 ∈ ℂ ↔ ∀ 𝑤𝑍 𝑤 / 𝑖 𝐶 ∈ ℂ ) )
111 104 110 bitr3id ( 𝜑 → ( ∀ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 ∈ ℂ ↔ ∀ 𝑤𝑍 𝑤 / 𝑖 𝐶 ∈ ℂ ) )
112 96 111 mpbid ( 𝜑 → ∀ 𝑤𝑍 𝑤 / 𝑖 𝐶 ∈ ℂ )
113 112 r19.21bi ( ( 𝜑𝑤𝑍 ) → 𝑤 / 𝑖 𝐶 ∈ ℂ )
114 71 73 74 76 113 fsumf1o ( 𝜑 → Σ 𝑤𝑍 𝑤 / 𝑖 𝐶 = Σ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 )
115 70 114 eqtrid ( 𝜑 → Σ 𝑖𝑍 𝐶 = Σ 𝑧 ∈ ( 𝑋 × 𝑌 ) ( ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ‘ 𝑧 ) / 𝑖 𝐶 )
116 54 66 115 3eqtr4a ( 𝜑 → Σ 𝑗𝑋 Σ 𝑘𝑌 𝐷 = Σ 𝑖𝑍 𝐶 )
117 22 29 116 3eqtrd ( 𝜑 → ( Σ 𝑗𝑋 𝐴 · Σ 𝑘𝑌 𝐵 ) = Σ 𝑖𝑍 𝐶 )