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 ovex ( 𝐶m ( 𝐴𝐵 ) ) ∈ V
2 1 a1i ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m ( 𝐴𝐵 ) ) ∈ V )
3 ovex ( 𝐶m 𝐴 ) ∈ V
4 ovex ( 𝐶m 𝐵 ) ∈ V
5 3 4 xpex ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ∈ V
6 5 a1i ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ∈ V )
7 elmapi ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶 )
8 ssun1 𝐴 ⊆ ( 𝐴𝐵 )
9 fssres ( ( 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶𝐴 ⊆ ( 𝐴𝐵 ) ) → ( 𝑥𝐴 ) : 𝐴𝐶 )
10 7 8 9 sylancl ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( 𝑥𝐴 ) : 𝐴𝐶 )
11 ssun2 𝐵 ⊆ ( 𝐴𝐵 )
12 fssres ( ( 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶𝐵 ⊆ ( 𝐴𝐵 ) ) → ( 𝑥𝐵 ) : 𝐵𝐶 )
13 7 11 12 sylancl ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( 𝑥𝐵 ) : 𝐵𝐶 )
14 10 13 jca ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( ( 𝑥𝐴 ) : 𝐴𝐶 ∧ ( 𝑥𝐵 ) : 𝐵𝐶 ) )
15 opelxp ( ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ↔ ( ( 𝑥𝐴 ) ∈ ( 𝐶m 𝐴 ) ∧ ( 𝑥𝐵 ) ∈ ( 𝐶m 𝐵 ) ) )
16 simpl3 ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → 𝐶𝑋 )
17 simpl1 ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → 𝐴𝑉 )
18 16 17 elmapd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝑥𝐴 ) ∈ ( 𝐶m 𝐴 ) ↔ ( 𝑥𝐴 ) : 𝐴𝐶 ) )
19 simpl2 ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → 𝐵𝑊 )
20 16 19 elmapd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝑥𝐵 ) ∈ ( 𝐶m 𝐵 ) ↔ ( 𝑥𝐵 ) : 𝐵𝐶 ) )
21 18 20 anbi12d ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( ( 𝑥𝐴 ) ∈ ( 𝐶m 𝐴 ) ∧ ( 𝑥𝐵 ) ∈ ( 𝐶m 𝐵 ) ) ↔ ( ( 𝑥𝐴 ) : 𝐴𝐶 ∧ ( 𝑥𝐵 ) : 𝐵𝐶 ) ) )
22 15 21 syl5bb ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ↔ ( ( 𝑥𝐴 ) : 𝐴𝐶 ∧ ( 𝑥𝐵 ) : 𝐵𝐶 ) ) )
23 14 22 syl5ibr ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) )
24 xp1st ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( 1st𝑦 ) ∈ ( 𝐶m 𝐴 ) )
25 24 adantl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 1st𝑦 ) ∈ ( 𝐶m 𝐴 ) )
26 elmapi ( ( 1st𝑦 ) ∈ ( 𝐶m 𝐴 ) → ( 1st𝑦 ) : 𝐴𝐶 )
27 25 26 syl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 1st𝑦 ) : 𝐴𝐶 )
28 xp2nd ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( 2nd𝑦 ) ∈ ( 𝐶m 𝐵 ) )
29 28 adantl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 2nd𝑦 ) ∈ ( 𝐶m 𝐵 ) )
30 elmapi ( ( 2nd𝑦 ) ∈ ( 𝐶m 𝐵 ) → ( 2nd𝑦 ) : 𝐵𝐶 )
31 29 30 syl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 2nd𝑦 ) : 𝐵𝐶 )
32 simplr ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 𝐴𝐵 ) = ∅ )
33 27 31 32 fun2d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) : ( 𝐴𝐵 ) ⟶ 𝐶 )
34 33 ex ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) : ( 𝐴𝐵 ) ⟶ 𝐶 ) )
35 unexg ( ( 𝐴𝑉𝐵𝑊 ) → ( 𝐴𝐵 ) ∈ V )
36 17 19 35 syl2anc ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐴𝐵 ) ∈ V )
37 16 36 elmapd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ∈ ( 𝐶m ( 𝐴𝐵 ) ) ↔ ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) : ( 𝐴𝐵 ) ⟶ 𝐶 ) )
38 34 37 sylibrd ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ∈ ( 𝐶m ( 𝐴𝐵 ) ) ) )
39 1st2nd2 ( 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) → 𝑦 = ⟨ ( 1st𝑦 ) , ( 2nd𝑦 ) ⟩ )
40 39 ad2antll ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → 𝑦 = ⟨ ( 1st𝑦 ) , ( 2nd𝑦 ) ⟩ )
41 27 adantrl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 1st𝑦 ) : 𝐴𝐶 )
42 31 adantrl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 2nd𝑦 ) : 𝐵𝐶 )
43 res0 ( ( 1st𝑦 ) ↾ ∅ ) = ∅
44 res0 ( ( 2nd𝑦 ) ↾ ∅ ) = ∅
45 43 44 eqtr4i ( ( 1st𝑦 ) ↾ ∅ ) = ( ( 2nd𝑦 ) ↾ ∅ )
46 simplr ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝐴𝐵 ) = ∅ )
47 46 reseq2d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 1st𝑦 ) ↾ ∅ ) )
48 46 reseq2d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ∅ ) )
49 45 47 48 3eqtr4a ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) )
50 fresaunres1 ( ( ( 1st𝑦 ) : 𝐴𝐶 ∧ ( 2nd𝑦 ) : 𝐵𝐶 ∧ ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) = ( 1st𝑦 ) )
51 41 42 49 50 syl3anc ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) = ( 1st𝑦 ) )
52 fresaunres2 ( ( ( 1st𝑦 ) : 𝐴𝐶 ∧ ( 2nd𝑦 ) : 𝐵𝐶 ∧ ( ( 1st𝑦 ) ↾ ( 𝐴𝐵 ) ) = ( ( 2nd𝑦 ) ↾ ( 𝐴𝐵 ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) = ( 2nd𝑦 ) )
53 41 42 49 52 syl3anc ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) = ( 2nd𝑦 ) )
54 51 53 opeq12d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ = ⟨ ( 1st𝑦 ) , ( 2nd𝑦 ) ⟩ )
55 40 54 eqtr4d ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → 𝑦 = ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ )
56 reseq1 ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ( 𝑥𝐴 ) = ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) )
57 reseq1 ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ( 𝑥𝐵 ) = ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) )
58 56 57 opeq12d ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ = ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ )
59 58 eqeq2d ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ↔ 𝑦 = ⟨ ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐴 ) , ( ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↾ 𝐵 ) ⟩ ) )
60 55 59 syl5ibrcom ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) → 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ) )
61 ffn ( 𝑥 : ( 𝐴𝐵 ) ⟶ 𝐶𝑥 Fn ( 𝐴𝐵 ) )
62 fnresdm ( 𝑥 Fn ( 𝐴𝐵 ) → ( 𝑥 ↾ ( 𝐴𝐵 ) ) = 𝑥 )
63 7 61 62 3syl ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) → ( 𝑥 ↾ ( 𝐴𝐵 ) ) = 𝑥 )
64 63 ad2antrl ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑥 ↾ ( 𝐴𝐵 ) ) = 𝑥 )
65 64 eqcomd ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → 𝑥 = ( 𝑥 ↾ ( 𝐴𝐵 ) ) )
66 vex 𝑥 ∈ V
67 66 resex ( 𝑥𝐴 ) ∈ V
68 66 resex ( 𝑥𝐵 ) ∈ V
69 67 68 op1std ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( 1st𝑦 ) = ( 𝑥𝐴 ) )
70 67 68 op2ndd ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( 2nd𝑦 ) = ( 𝑥𝐵 ) )
71 69 70 uneq12d ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) = ( ( 𝑥𝐴 ) ∪ ( 𝑥𝐵 ) ) )
72 resundi ( 𝑥 ↾ ( 𝐴𝐵 ) ) = ( ( 𝑥𝐴 ) ∪ ( 𝑥𝐵 ) )
73 71 72 syl6eqr ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) = ( 𝑥 ↾ ( 𝐴𝐵 ) ) )
74 73 eqeq2d ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↔ 𝑥 = ( 𝑥 ↾ ( 𝐴𝐵 ) ) ) )
75 65 74 syl5ibrcom ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ → 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ) )
76 60 75 impbid ( ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) ∧ ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) ) → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↔ 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ) )
77 76 ex ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( ( 𝑥 ∈ ( 𝐶m ( 𝐴𝐵 ) ) ∧ 𝑦 ∈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) ) → ( 𝑥 = ( ( 1st𝑦 ) ∪ ( 2nd𝑦 ) ) ↔ 𝑦 = ⟨ ( 𝑥𝐴 ) , ( 𝑥𝐵 ) ⟩ ) ) )
78 2 6 23 38 77 en3d ( ( ( 𝐴𝑉𝐵𝑊𝐶𝑋 ) ∧ ( 𝐴𝐵 ) = ∅ ) → ( 𝐶m ( 𝐴𝐵 ) ) ≈ ( ( 𝐶m 𝐴 ) × ( 𝐶m 𝐵 ) ) )