| Step | Hyp | Ref
 | Expression | 
| 1 |   | df-domfn 5771 | 
. . 3
⊢  Dom = (x ∈ V ↦ dom
x) | 
| 2 |   | elin 3220 | 
. . . . . . . . 9
⊢ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ ( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) ↔ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins4 SI3  Swap
 ∧ 〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins2 Ins2  S )) | 
| 3 |   | vex 2863 | 
. . . . . . . . . . . 12
⊢ x ∈
V | 
| 4 | 3 | oqelins4 5795 | 
. . . . . . . . . . 11
⊢ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins4 SI3  Swap
 ↔ 〈{w}, 〈{z}, {y}〉〉 ∈ SI3  Swap
) | 
| 5 |   | vex 2863 | 
. . . . . . . . . . . . 13
⊢ w ∈
V | 
| 6 |   | vex 2863 | 
. . . . . . . . . . . . 13
⊢ z ∈
V | 
| 7 |   | vex 2863 | 
. . . . . . . . . . . . 13
⊢ y ∈
V | 
| 8 | 5, 6, 7 | otsnelsi3 5806 | 
. . . . . . . . . . . 12
⊢ (〈{w}, 〈{z}, {y}〉〉 ∈ SI3  Swap
 ↔ 〈w, 〈z, y〉〉 ∈  Swap
) | 
| 9 |   | df-br 4641 | 
. . . . . . . . . . . 12
⊢ (w Swap 〈z, y〉 ↔ 〈w, 〈z, y〉〉 ∈  Swap ) | 
| 10 | 6, 7 | brswap2 4861 | 
. . . . . . . . . . . 12
⊢ (w Swap 〈z, y〉 ↔ w = 〈y, z〉) | 
| 11 | 8, 9, 10 | 3bitr2i 264 | 
. . . . . . . . . . 11
⊢ (〈{w}, 〈{z}, {y}〉〉 ∈ SI3  Swap
 ↔ w = 〈y, z〉) | 
| 12 | 4, 11 | bitri 240 | 
. . . . . . . . . 10
⊢ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins4 SI3  Swap
 ↔ w = 〈y, z〉) | 
| 13 |   | snex 4112 | 
. . . . . . . . . . . 12
⊢ {z} ∈
V | 
| 14 | 13 | otelins2 5792 | 
. . . . . . . . . . 11
⊢ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins2 Ins2  S  ↔ 〈{w}, 〈{y}, x〉〉 ∈ Ins2  S ) | 
| 15 |   | snex 4112 | 
. . . . . . . . . . . . 13
⊢ {y} ∈
V | 
| 16 | 15 | otelins2 5792 | 
. . . . . . . . . . . 12
⊢ (〈{w}, 〈{y}, x〉〉 ∈ Ins2  S  ↔ 〈{w}, x〉 ∈  S
) | 
| 17 | 5, 3 | opelssetsn 4761 | 
. . . . . . . . . . . 12
⊢ (〈{w}, x〉 ∈  S  ↔ w ∈ x) | 
| 18 | 16, 17 | bitri 240 | 
. . . . . . . . . . 11
⊢ (〈{w}, 〈{y}, x〉〉 ∈ Ins2  S  ↔ w ∈ x) | 
| 19 | 14, 18 | bitri 240 | 
. . . . . . . . . 10
⊢ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins2 Ins2  S  ↔ w ∈ x) | 
| 20 | 12, 19 | anbi12i 678 | 
. . . . . . . . 9
⊢ ((〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins4 SI3  Swap
 ∧ 〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ Ins2 Ins2  S ) ↔ (w = 〈y, z〉 ∧ w ∈ x)) | 
| 21 | 2, 20 | bitri 240 | 
. . . . . . . 8
⊢ (〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ ( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) ↔ (w = 〈y, z〉 ∧ w ∈ x)) | 
| 22 | 21 | exbii 1582 | 
. . . . . . 7
⊢ (∃w〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ ( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) ↔ ∃w(w = 〈y, z〉 ∧ w ∈ x)) | 
| 23 |   | elima1c 4948 | 
. . . . . . 7
⊢ (〈{z}, 〈{y}, x〉〉 ∈ (( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) “
1c) ↔ ∃w〈{w}, 〈{z}, 〈{y}, x〉〉〉 ∈ ( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S
)) | 
| 24 |   | df-clel 2349 | 
. . . . . . 7
⊢ (〈y, z〉 ∈ x ↔
∃w(w = 〈y, z〉 ∧ w ∈ x)) | 
| 25 | 22, 23, 24 | 3bitr4i 268 | 
. . . . . 6
⊢ (〈{z}, 〈{y}, x〉〉 ∈ (( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) “
1c) ↔ 〈y, z〉 ∈ x) | 
| 26 | 25 | exbii 1582 | 
. . . . 5
⊢ (∃z〈{z}, 〈{y}, x〉〉 ∈ (( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) “
1c) ↔ ∃z〈y, z〉 ∈ x) | 
| 27 |   | elima1c 4948 | 
. . . . 5
⊢ (〈{y}, x〉 ∈ ((( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) “
1c) “ 1c) ↔ ∃z〈{z}, 〈{y}, x〉〉 ∈ (( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) “
1c)) | 
| 28 |   | eldm2 4900 | 
. . . . 5
⊢ (y ∈ dom x ↔ ∃z〈y, z〉 ∈ x) | 
| 29 | 26, 27, 28 | 3bitr4i 268 | 
. . . 4
⊢ (〈{y}, x〉 ∈ ((( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) “
1c) “ 1c) ↔ y ∈ dom x) | 
| 30 | 29 | releqmpt 5809 | 
. . 3
⊢ ((V × V)
∩ ◡ ∼ (( Ins3  S  ⊕ Ins2 ((( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) “
1c) “ 1c)) “
1c)) = (x ∈ V ↦ dom
x) | 
| 31 | 1, 30 | eqtr4i 2376 | 
. 2
⊢  Dom = ((V × V) ∩ ◡ ∼ (( Ins3
 S  ⊕ Ins2 (((
Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) “
1c) “ 1c)) “
1c)) | 
| 32 |   | vvex 4110 | 
. . 3
⊢ V ∈ V | 
| 33 |   | swapex 4743 | 
. . . . . . . 8
⊢  Swap  ∈
V | 
| 34 | 33 | si3ex 5807 | 
. . . . . . 7
⊢  SI3  Swap
 ∈ V | 
| 35 | 34 | ins4ex 5800 | 
. . . . . 6
⊢  Ins4 SI3
 Swap  ∈
V | 
| 36 |   | ssetex 4745 | 
. . . . . . . 8
⊢  S  ∈
V | 
| 37 | 36 | ins2ex 5798 | 
. . . . . . 7
⊢  Ins2  S  ∈ V | 
| 38 | 37 | ins2ex 5798 | 
. . . . . 6
⊢  Ins2 Ins2  S  ∈
V | 
| 39 | 35, 38 | inex 4106 | 
. . . . 5
⊢ ( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) ∈ V | 
| 40 |   | 1cex 4143 | 
. . . . 5
⊢
1c ∈
V | 
| 41 | 39, 40 | imaex 4748 | 
. . . 4
⊢ (( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) “
1c) ∈ V | 
| 42 | 41, 40 | imaex 4748 | 
. . 3
⊢ ((( Ins4 SI3
 Swap  ∩ Ins2
Ins2  S ) “
1c) “ 1c) ∈ V | 
| 43 | 32, 42 | mptexlem 5811 | 
. 2
⊢ ((V × V)
∩ ◡ ∼ (( Ins3  S  ⊕ Ins2 ((( Ins4 SI3  Swap
 ∩ Ins2 Ins2  S ) “
1c) “ 1c)) “
1c)) ∈ V | 
| 44 | 31, 43 | eqeltri 2423 | 
1
⊢  Dom ∈
V |