Proof of Theorem opkthg
| Step | Hyp | Ref
 | Expression | 
| 1 |   | simp1 955 | 
. . . . 5
⊢ ((A ∈ V ∧ B ∈ W ∧ D ∈ T) → A
∈ V) | 
| 2 |   | opkth1g 4131 | 
. . . . 5
⊢ ((A ∈ V ∧
⟪A, B⟫ = ⟪C, D⟫)
→ A = C) | 
| 3 | 1, 2 | sylan 457 | 
. . . 4
⊢ (((A ∈ V ∧ B ∈ W ∧ D ∈ T) ∧
⟪A, B⟫ = ⟪C, D⟫)
→ A = C) | 
| 4 |   | simp2 956 | 
. . . . . 6
⊢ ((A ∈ V ∧ B ∈ W ∧ D ∈ T) → B
∈ W) | 
| 5 |   | simp3 957 | 
. . . . . 6
⊢ ((A ∈ V ∧ B ∈ W ∧ D ∈ T) → D
∈ T) | 
| 6 | 4, 5 | jca 518 | 
. . . . 5
⊢ ((A ∈ V ∧ B ∈ W ∧ D ∈ T) → (B
∈ W ∧ D ∈ T)) | 
| 7 |   | opkeq1 4060 | 
. . . . . . . . . . 11
⊢ (A = C →
⟪A, B⟫ = ⟪C, B⟫) | 
| 8 | 7 | eqeq1d 2361 | 
. . . . . . . . . 10
⊢ (A = C →
(⟪A, B⟫ = ⟪C, D⟫
↔ ⟪C, B⟫ = ⟪C, D⟫)) | 
| 9 | 8 | biimpd 198 | 
. . . . . . . . 9
⊢ (A = C →
(⟪A, B⟫ = ⟪C, D⟫
→ ⟪C, B⟫ = ⟪C, D⟫)) | 
| 10 | 9 | impcom 419 | 
. . . . . . . 8
⊢ ((⟪A, B⟫ =
⟪C, D⟫ ∧
A = C)
→ ⟪C, B⟫ = ⟪C, D⟫) | 
| 11 |   | df-opk 4059 | 
. . . . . . . . . . 11
⊢ ⟪C, B⟫ =
{{C}, {C, B}} | 
| 12 |   | df-opk 4059 | 
. . . . . . . . . . 11
⊢ ⟪C, D⟫ =
{{C}, {C, D}} | 
| 13 | 11, 12 | eqeq12i 2366 | 
. . . . . . . . . 10
⊢ (⟪C, B⟫ =
⟪C, D⟫ ↔ {{C}, {C, B}} = {{C},
{C, D}}) | 
| 14 |   | prex 4113 | 
. . . . . . . . . . 11
⊢ {C, B} ∈ V | 
| 15 |   | prex 4113 | 
. . . . . . . . . . 11
⊢ {C, D} ∈ V | 
| 16 | 14, 15 | preqr2 4126 | 
. . . . . . . . . 10
⊢ ({{C}, {C, B}} = {{C},
{C, D}}
→ {C, B} = {C,
D}) | 
| 17 | 13, 16 | sylbi 187 | 
. . . . . . . . 9
⊢ (⟪C, B⟫ =
⟪C, D⟫ → {C, B} =
{C, D}) | 
| 18 |   | preqr2g 4127 | 
. . . . . . . . 9
⊢ ((B ∈ W ∧ D ∈ T) → ({C,
B} = {C, D} →
B = D)) | 
| 19 | 17, 18 | syl5 28 | 
. . . . . . . 8
⊢ ((B ∈ W ∧ D ∈ T) → (⟪C, B⟫ =
⟪C, D⟫ → B = D)) | 
| 20 | 10, 19 | syl5 28 | 
. . . . . . 7
⊢ ((B ∈ W ∧ D ∈ T) → ((⟪A, B⟫ =
⟪C, D⟫ ∧
A = C)
→ B = D)) | 
| 21 | 20 | exp3a 425 | 
. . . . . 6
⊢ ((B ∈ W ∧ D ∈ T) → (⟪A, B⟫ =
⟪C, D⟫ → (A = C →
B = D))) | 
| 22 | 21 | imp 418 | 
. . . . 5
⊢ (((B ∈ W ∧ D ∈ T) ∧
⟪A, B⟫ = ⟪C, D⟫)
→ (A = C → B =
D)) | 
| 23 | 6, 22 | sylan 457 | 
. . . 4
⊢ (((A ∈ V ∧ B ∈ W ∧ D ∈ T) ∧
⟪A, B⟫ = ⟪C, D⟫)
→ (A = C → B =
D)) | 
| 24 | 3, 23 | jcai 522 | 
. . 3
⊢ (((A ∈ V ∧ B ∈ W ∧ D ∈ T) ∧
⟪A, B⟫ = ⟪C, D⟫)
→ (A = C ∧ B = D)) | 
| 25 | 24 | ex 423 | 
. 2
⊢ ((A ∈ V ∧ B ∈ W ∧ D ∈ T) → (⟪A, B⟫ =
⟪C, D⟫ → (A = C ∧ B = D))) | 
| 26 |   | opkeq12 4062 | 
. 2
⊢ ((A = C ∧ B = D) → ⟪A, B⟫ =
⟪C, D⟫) | 
| 27 | 25, 26 | impbid1 194 | 
1
⊢ ((A ∈ V ∧ B ∈ W ∧ D ∈ T) → (⟪A, B⟫ =
⟪C, D⟫ ↔ (A = C ∧ B = D))) |