| Step | Hyp | Ref | Expression | 
|---|
| 1 |  | frege77.x | . . 3
⊢ 𝑋 ∈ 𝑈 | 
| 2 |  | frege77.y | . . 3
⊢ 𝑌 ∈ 𝑉 | 
| 3 |  | frege77.r | . . 3
⊢ 𝑅 ∈ 𝑊 | 
| 4 | 1, 2, 3 | dffrege76 43952 | . 2
⊢
(∀𝑓(𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ 𝑋(t+‘𝑅)𝑌) | 
| 5 |  | frege77.a | . . . 4
⊢ 𝐴 ∈ 𝐵 | 
| 6 | 5 | frege68c 43944 | . . 3
⊢
((∀𝑓(𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ 𝑋(t+‘𝑅)𝑌) → (𝑋(t+‘𝑅)𝑌 → [𝐴 / 𝑓](𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)))) | 
| 7 |  | sbcimg 3837 | . . . . 5
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓](𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ ([𝐴 / 𝑓]𝑅 hereditary 𝑓 → [𝐴 / 𝑓](∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)))) | 
| 8 | 5, 7 | ax-mp 5 | . . . 4
⊢
([𝐴 / 𝑓](𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ ([𝐴 / 𝑓]𝑅 hereditary 𝑓 → [𝐴 / 𝑓](∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓))) | 
| 9 |  | sbcheg 43792 | . . . . . . 7
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓]𝑅 hereditary 𝑓 ↔ ⦋𝐴 / 𝑓⦌𝑅 hereditary ⦋𝐴 / 𝑓⦌𝑓)) | 
| 10 | 5, 9 | ax-mp 5 | . . . . . 6
⊢
([𝐴 / 𝑓]𝑅 hereditary 𝑓 ↔ ⦋𝐴 / 𝑓⦌𝑅 hereditary ⦋𝐴 / 𝑓⦌𝑓) | 
| 11 |  | csbconstg 3918 | . . . . . . . 8
⊢ (𝐴 ∈ 𝐵 → ⦋𝐴 / 𝑓⦌𝑅 = 𝑅) | 
| 12 | 5, 11 | ax-mp 5 | . . . . . . 7
⊢
⦋𝐴 /
𝑓⦌𝑅 = 𝑅 | 
| 13 |  | csbvarg 4434 | . . . . . . . 8
⊢ (𝐴 ∈ 𝐵 → ⦋𝐴 / 𝑓⦌𝑓 = 𝐴) | 
| 14 | 5, 13 | ax-mp 5 | . . . . . . 7
⊢
⦋𝐴 /
𝑓⦌𝑓 = 𝐴 | 
| 15 |  | heeq12 43789 | . . . . . . 7
⊢
((⦋𝐴 /
𝑓⦌𝑅 = 𝑅 ∧ ⦋𝐴 / 𝑓⦌𝑓 = 𝐴) → (⦋𝐴 / 𝑓⦌𝑅 hereditary ⦋𝐴 / 𝑓⦌𝑓 ↔ 𝑅 hereditary 𝐴)) | 
| 16 | 12, 14, 15 | mp2an 692 | . . . . . 6
⊢
(⦋𝐴 /
𝑓⦌𝑅 hereditary ⦋𝐴 / 𝑓⦌𝑓 ↔ 𝑅 hereditary 𝐴) | 
| 17 | 10, 16 | bitri 275 | . . . . 5
⊢
([𝐴 / 𝑓]𝑅 hereditary 𝑓 ↔ 𝑅 hereditary 𝐴) | 
| 18 |  | sbcimg 3837 | . . . . . . 7
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓](∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓) ↔ ([𝐴 / 𝑓]∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → [𝐴 / 𝑓]𝑌 ∈ 𝑓))) | 
| 19 | 5, 18 | ax-mp 5 | . . . . . 6
⊢
([𝐴 / 𝑓](∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓) ↔ ([𝐴 / 𝑓]∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → [𝐴 / 𝑓]𝑌 ∈ 𝑓)) | 
| 20 |  | sbcal 3849 | . . . . . . . 8
⊢
([𝐴 / 𝑓]∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) ↔ ∀𝑎[𝐴 / 𝑓](𝑋𝑅𝑎 → 𝑎 ∈ 𝑓)) | 
| 21 |  | sbcimg 3837 | . . . . . . . . . . 11
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓](𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) ↔ ([𝐴 / 𝑓]𝑋𝑅𝑎 → [𝐴 / 𝑓]𝑎 ∈ 𝑓))) | 
| 22 | 5, 21 | ax-mp 5 | . . . . . . . . . 10
⊢
([𝐴 / 𝑓](𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) ↔ ([𝐴 / 𝑓]𝑋𝑅𝑎 → [𝐴 / 𝑓]𝑎 ∈ 𝑓)) | 
| 23 |  | sbcg 3863 | . . . . . . . . . . . 12
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓]𝑋𝑅𝑎 ↔ 𝑋𝑅𝑎)) | 
| 24 | 5, 23 | ax-mp 5 | . . . . . . . . . . 11
⊢
([𝐴 / 𝑓]𝑋𝑅𝑎 ↔ 𝑋𝑅𝑎) | 
| 25 |  | sbcel2gv 3857 | . . . . . . . . . . . 12
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓]𝑎 ∈ 𝑓 ↔ 𝑎 ∈ 𝐴)) | 
| 26 | 5, 25 | ax-mp 5 | . . . . . . . . . . 11
⊢
([𝐴 / 𝑓]𝑎 ∈ 𝑓 ↔ 𝑎 ∈ 𝐴) | 
| 27 | 24, 26 | imbi12i 350 | . . . . . . . . . 10
⊢
(([𝐴 / 𝑓]𝑋𝑅𝑎 → [𝐴 / 𝑓]𝑎 ∈ 𝑓) ↔ (𝑋𝑅𝑎 → 𝑎 ∈ 𝐴)) | 
| 28 | 22, 27 | bitri 275 | . . . . . . . . 9
⊢
([𝐴 / 𝑓](𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) ↔ (𝑋𝑅𝑎 → 𝑎 ∈ 𝐴)) | 
| 29 | 28 | albii 1819 | . . . . . . . 8
⊢
(∀𝑎[𝐴 / 𝑓](𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) ↔ ∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴)) | 
| 30 | 20, 29 | bitri 275 | . . . . . . 7
⊢
([𝐴 / 𝑓]∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) ↔ ∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴)) | 
| 31 |  | sbcel2gv 3857 | . . . . . . . 8
⊢ (𝐴 ∈ 𝐵 → ([𝐴 / 𝑓]𝑌 ∈ 𝑓 ↔ 𝑌 ∈ 𝐴)) | 
| 32 | 5, 31 | ax-mp 5 | . . . . . . 7
⊢
([𝐴 / 𝑓]𝑌 ∈ 𝑓 ↔ 𝑌 ∈ 𝐴) | 
| 33 | 30, 32 | imbi12i 350 | . . . . . 6
⊢
(([𝐴 / 𝑓]∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → [𝐴 / 𝑓]𝑌 ∈ 𝑓) ↔ (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴) → 𝑌 ∈ 𝐴)) | 
| 34 | 19, 33 | bitri 275 | . . . . 5
⊢
([𝐴 / 𝑓](∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓) ↔ (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴) → 𝑌 ∈ 𝐴)) | 
| 35 | 17, 34 | imbi12i 350 | . . . 4
⊢
(([𝐴 / 𝑓]𝑅 hereditary 𝑓 → [𝐴 / 𝑓](∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ (𝑅 hereditary 𝐴 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴) → 𝑌 ∈ 𝐴))) | 
| 36 | 8, 35 | bitri 275 | . . 3
⊢
([𝐴 / 𝑓](𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ (𝑅 hereditary 𝐴 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴) → 𝑌 ∈ 𝐴))) | 
| 37 | 6, 36 | imbitrdi 251 | . 2
⊢
((∀𝑓(𝑅 hereditary 𝑓 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝑓) → 𝑌 ∈ 𝑓)) ↔ 𝑋(t+‘𝑅)𝑌) → (𝑋(t+‘𝑅)𝑌 → (𝑅 hereditary 𝐴 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴) → 𝑌 ∈ 𝐴)))) | 
| 38 | 4, 37 | ax-mp 5 | 1
⊢ (𝑋(t+‘𝑅)𝑌 → (𝑅 hereditary 𝐴 → (∀𝑎(𝑋𝑅𝑎 → 𝑎 ∈ 𝐴) → 𝑌 ∈ 𝐴))) |