Metamath Proof Explorer


Theorem mapunen

Description: Equinumerosity law for set exponentiation of a disjoint union. Exercise 4.45 of Mendelson p. 255. (Contributed by NM, 23-Sep-2004) (Revised by Mario Carneiro, 29-Apr-2015)

Ref Expression
Assertion mapunen ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m ( 𝐴𝐵 ) ) ≈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) )

Proof

Step Hyp Ref Expression
1 ovexd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m ( 𝐴𝐵 ) ) ∈ V )
2 ovexd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m 𝐴 ) ∈ V )
3 ovexd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m 𝐵 ) ∈ V )
4 2 3 xpexd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ∈ V )
5 elmapi ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶 )
6 ssun1 𝐴 ⊆ ( 𝐴𝐵 )
7 fssres ( ( 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶𝐴 ⊆ ( 𝐴𝐵 ) ) → ( 𝑥𝐴 ) : 𝐴𝐶 )
8 5 6 7 sylancl ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( 𝑥𝐴 ) : 𝐴𝐶 )
9 ssun2 𝐵 ⊆ ( 𝐴𝐵 )
10 fssres ( ( 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶𝐵 ⊆ ( 𝐴𝐵 ) ) → ( 𝑥𝐵 ) : 𝐵𝐶 )
11 5 9 10 sylancl ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( 𝑥𝐵 ) : 𝐵𝐶 )
12 8 11 jca ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( ( 𝑥𝐴 ) : 𝐴𝐶 ∧ ( 𝑥𝐵 ) : 𝐵𝐶 ) )
13 opelxp ( ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ↔ ( ( 𝑥𝐴 ) ∈ ( 𝐶m 𝐴 ) ∧ ( 𝑥𝐵 ) ∈ ( 𝐶m 𝐵 ) ) )
14 simpl3 ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → 𝐶𝑋 )
15 simpl1 ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → 𝐴𝑉 )
16 14 15 elmapd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝑥𝐴 ) ∈ ( 𝐶m 𝐴 ) ↔ ( 𝑥𝐴 ) : 𝐴𝐶 ) )
17 simpl2 ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → 𝐵𝑊 )
18 14 17 elmapd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝑥𝐵 ) ∈ ( 𝐶m 𝐵 ) ↔ ( 𝑥𝐵 ) : 𝐵𝐶 ) )
19 16 18 anbi12d ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( ( 𝑥𝐴 ) ∈ ( 𝐶m 𝐴 ) ∧ ( 𝑥𝐵 ) ∈ ( 𝐶m 𝐵 ) ) ↔ ( ( 𝑥𝐴 ) : 𝐴𝐶 ∧ ( 𝑥𝐵 ) : 𝐵𝐶 ) ) )
20 13 19 bitrid ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ↔ ( ( 𝑥𝐴 ) : 𝐴𝐶 ∧ ( 𝑥𝐵 ) : 𝐵𝐶 ) ) )
21 12 20 imbitrrid ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) )
22 xp1st ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( 1st𝑦 ) ∈ ( 𝐶m 𝐴 ) )
23 22 adantl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 1st𝑦 ) ∈ ( 𝐶m 𝐴 ) )
24 elmapi ( ( 1st𝑦 ) ∈ ( 𝐶m 𝐴 ) → ( 1st𝑦 ) : 𝐴𝐶 )
25 23 24 syl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 1st𝑦 ) : 𝐴𝐶 )
26 xp2nd ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( 2nd𝑦 ) ∈ ( 𝐶m 𝐵 ) )
27 26 adantl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 2nd𝑦 ) ∈ ( 𝐶m 𝐵 ) )
28 elmapi ( ( 2nd𝑦 ) ∈ ( 𝐶m 𝐵 ) → ( 2nd𝑦 ) : 𝐵𝐶 )
29 27 28 syl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 2nd𝑦 ) : 𝐵𝐶 )
30 simplr ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 𝐴𝐵 ) = ∅ )
31 25 29 30 fun2d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) : ( 𝐴𝐵 ) ⟶ 𝐶 )
32 31 ex ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) : ( 𝐴𝐵 ) ⟶ 𝐶 ) )
33 15 17 unexd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐴𝐵 ) ∈ V )
34 14 33 elmapd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ∈ ( 𝐶m ( 𝐴𝐵 ) ) ↔ ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) : ( 𝐴𝐵 ) ⟶ 𝐶 ) )
35 32 34 sylibrd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ∈ ( 𝐶m ( 𝐴𝐵 ) ) ) )
36 1st2nd2 ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → 𝑦 = ⟨ ( 1st𝑦 ) , ( 2nd𝑦 ) ⟩ )
37 36 ad2antll ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → 𝑦 = ⟨ ( 1st𝑦 ) , ( 2nd𝑦 ) ⟩ )
38 25 adantrl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 1st𝑦 ) : 𝐴𝐶 )
39 29 adantrl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 2nd𝑦 ) : 𝐵𝐶 )
40 res0 ( ( 1st𝑦 ) ↾ ∅ ) = ∅
41 res0 ( ( 2nd𝑦 ) ↾ ∅ ) = ∅
42 40 41 eqtr4i ( ( 1st𝑦 ) ↾ ∅ ) = ( ( 2nd𝑦 ) ↾ ∅ )
43 simplr ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝐴𝐵 ) = ∅ )
44 43 reseq2d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 1st𝑦 ) ↾ ∅ ) )
45 43 reseq2d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ∅ ) )
46 42 44 45 3eqtr4a ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) )
47 fresaunres1 ( ( ( 1st𝑦 ) : 𝐴𝐶 ∧ ( 2nd𝑦 ) : 𝐵𝐶 ∧ ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) = ( 1st𝑦 ) )
48 38 39 46 47 syl3anc ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) = ( 1st𝑦 ) )
49 fresaunres2 ( ( ( 1st𝑦 ) : 𝐴𝐶 ∧ ( 2nd𝑦 ) : 𝐵𝐶 ∧ ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) = ( 2nd𝑦 ) )
50 38 39 46 49 syl3anc ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) = ( 2nd𝑦 ) )
51 48 50 opeq12d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ = ⟨ ( 1st𝑦 ) , ( 2nd𝑦 ) ⟩ )
52 37 51 eqtr4d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → 𝑦 = ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ )
53 reseq1 ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ( 𝑥𝐴 ) = ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) )
54 reseq1 ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ( 𝑥𝐵 ) = ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) )
55 53 54 opeq12d ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ = ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ )
56 55 eqeq2d ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ↔ 𝑦 = ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ ) )
57 52 56 syl5ibrcom ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ) )
58 ffn ( 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶𝑥 Fn ( 𝐴𝐵 ) )
59 fnresdm ( 𝑥 Fn ( 𝐴𝐵 ) → ( 𝑥 ↾ ( 𝐴𝐵 ) ) = 𝑥 )
60 5 58 59 3syl ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( 𝑥 ↾ ( 𝐴𝐵 ) ) = 𝑥 )
61 60 ad2antrl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑥 ↾ ( 𝐴𝐵 ) ) = 𝑥 )
62 61 eqcomd ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → 𝑥 = ( 𝑥 ↾ ( 𝐴𝐵 ) ) )
63 vex 𝑥 ∈ V
64 63 resex ( 𝑥𝐴 ) ∈ V
65 63 resex ( 𝑥𝐵 ) ∈ V
66 64 65 op1std ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( 1st𝑦 ) = ( 𝑥𝐴 ) )
67 64 65 op2ndd ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( 2nd𝑦 ) = ( 𝑥𝐵 ) )
68 66 67 uneq12d ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) = ( ( 𝑥𝐴 ) ∪ ( 𝑥𝐵 ) ) )
69 resundi ( 𝑥 ↾ ( 𝐴𝐵 ) ) = ( ( 𝑥𝐴 ) ∪ ( 𝑥𝐵 ) )
70 68 69 eqtr4di ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) = ( 𝑥 ↾ ( 𝐴𝐵 ) ) )
71 70 eqeq2d ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↔ 𝑥 = ( 𝑥 ↾ ( 𝐴𝐵 ) ) ) )
72 62 71 syl5ibrcom ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ) )
73 57 72 impbid ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↔ 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ) )
74 73 ex ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↔ 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ) ) )
75 1 4 21 35 74 en3d ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m ( 𝐴𝐵 ) ) ≈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) )