Proof of Theorem fzass4
| Step | Hyp | Ref | Expression | 
|---|
| 1 |  | simpll 767 | . . . . 5
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐵 ∈ (ℤ≥‘𝐴)) | 
| 2 |  | simprl 771 | . . . . 5
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐶 ∈ (ℤ≥‘𝐵)) | 
| 3 | 1, 2 | jca 511 | . . . 4
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → (𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵))) | 
| 4 |  | uztrn 12896 | . . . . . 6
⊢ ((𝐶 ∈
(ℤ≥‘𝐵) ∧ 𝐵 ∈ (ℤ≥‘𝐴)) → 𝐶 ∈ (ℤ≥‘𝐴)) | 
| 5 | 4 | ancoms 458 | . . . . 5
⊢ ((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) → 𝐶 ∈ (ℤ≥‘𝐴)) | 
| 6 | 5 | ad2ant2r 747 | . . . 4
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐶 ∈ (ℤ≥‘𝐴)) | 
| 7 |  | simprr 773 | . . . 4
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐷 ∈ (ℤ≥‘𝐶)) | 
| 8 | 3, 6, 7 | jca32 515 | . . 3
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → ((𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶)))) | 
| 9 |  | simpll 767 | . . . . 5
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐵 ∈ (ℤ≥‘𝐴)) | 
| 10 |  | uztrn 12896 | . . . . . . 7
⊢ ((𝐷 ∈
(ℤ≥‘𝐶) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) → 𝐷 ∈ (ℤ≥‘𝐵)) | 
| 11 | 10 | ancoms 458 | . . . . . 6
⊢ ((𝐶 ∈
(ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶)) → 𝐷 ∈ (ℤ≥‘𝐵)) | 
| 12 | 11 | ad2ant2l 746 | . . . . 5
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐷 ∈ (ℤ≥‘𝐵)) | 
| 13 | 9, 12 | jca 511 | . . . 4
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → (𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵))) | 
| 14 |  | simplr 769 | . . . 4
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐶 ∈ (ℤ≥‘𝐵)) | 
| 15 |  | simprr 773 | . . . 4
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → 𝐷 ∈ (ℤ≥‘𝐶)) | 
| 16 | 13, 14, 15 | jca32 515 | . . 3
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) → ((𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶)))) | 
| 17 | 8, 16 | impbii 209 | . 2
⊢ (((𝐵 ∈
(ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) ↔ ((𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶)))) | 
| 18 |  | elfzuzb 13558 | . . 3
⊢ (𝐵 ∈ (𝐴...𝐷) ↔ (𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵))) | 
| 19 |  | elfzuzb 13558 | . . 3
⊢ (𝐶 ∈ (𝐵...𝐷) ↔ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) | 
| 20 | 18, 19 | anbi12i 628 | . 2
⊢ ((𝐵 ∈ (𝐴...𝐷) ∧ 𝐶 ∈ (𝐵...𝐷)) ↔ ((𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐵) ∧ 𝐷 ∈ (ℤ≥‘𝐶)))) | 
| 21 |  | elfzuzb 13558 | . . 3
⊢ (𝐵 ∈ (𝐴...𝐶) ↔ (𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵))) | 
| 22 |  | elfzuzb 13558 | . . 3
⊢ (𝐶 ∈ (𝐴...𝐷) ↔ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶))) | 
| 23 | 21, 22 | anbi12i 628 | . 2
⊢ ((𝐵 ∈ (𝐴...𝐶) ∧ 𝐶 ∈ (𝐴...𝐷)) ↔ ((𝐵 ∈ (ℤ≥‘𝐴) ∧ 𝐶 ∈ (ℤ≥‘𝐵)) ∧ (𝐶 ∈ (ℤ≥‘𝐴) ∧ 𝐷 ∈ (ℤ≥‘𝐶)))) | 
| 24 | 17, 20, 23 | 3bitr4i 303 | 1
⊢ ((𝐵 ∈ (𝐴...𝐷) ∧ 𝐶 ∈ (𝐵...𝐷)) ↔ (𝐵 ∈ (𝐴...𝐶) ∧ 𝐶 ∈ (𝐴...𝐷))) |