Proof of Theorem sbcoteq1a
| Step | Hyp | Ref | Expression | 
|---|
| 1 |  | fveq2 6906 | . . . 4
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → (2nd ‘𝐴) = (2nd
‘〈𝑥, 𝑦, 𝑧〉)) | 
| 2 |  | ot3rdg 8030 | . . . . 5
⊢ (𝑧 ∈ V → (2nd
‘〈𝑥, 𝑦, 𝑧〉) = 𝑧) | 
| 3 | 2 | elv 3485 | . . . 4
⊢
(2nd ‘〈𝑥, 𝑦, 𝑧〉) = 𝑧 | 
| 4 | 1, 3 | eqtr2di 2794 | . . 3
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → 𝑧 = (2nd ‘𝐴)) | 
| 5 |  | sbceq1a 3799 | . . 3
⊢ (𝑧 = (2nd ‘𝐴) → (𝜑 ↔ [(2nd ‘𝐴) / 𝑧]𝜑)) | 
| 6 | 4, 5 | syl 17 | . 2
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → (𝜑 ↔ [(2nd ‘𝐴) / 𝑧]𝜑)) | 
| 7 |  | 2fveq3 6911 | . . . 4
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → (2nd
‘(1st ‘𝐴)) = (2nd ‘(1st
‘〈𝑥, 𝑦, 𝑧〉))) | 
| 8 |  | vex 3484 | . . . . 5
⊢ 𝑥 ∈ V | 
| 9 |  | vex 3484 | . . . . 5
⊢ 𝑦 ∈ V | 
| 10 |  | vex 3484 | . . . . 5
⊢ 𝑧 ∈ V | 
| 11 |  | ot2ndg 8029 | . . . . 5
⊢ ((𝑥 ∈ V ∧ 𝑦 ∈ V ∧ 𝑧 ∈ V) →
(2nd ‘(1st ‘〈𝑥, 𝑦, 𝑧〉)) = 𝑦) | 
| 12 | 8, 9, 10, 11 | mp3an 1463 | . . . 4
⊢
(2nd ‘(1st ‘〈𝑥, 𝑦, 𝑧〉)) = 𝑦 | 
| 13 | 7, 12 | eqtr2di 2794 | . . 3
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → 𝑦 = (2nd ‘(1st
‘𝐴))) | 
| 14 |  | sbceq1a 3799 | . . 3
⊢ (𝑦 = (2nd
‘(1st ‘𝐴)) → ([(2nd
‘𝐴) / 𝑧]𝜑 ↔ [(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑)) | 
| 15 | 13, 14 | syl 17 | . 2
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → ([(2nd
‘𝐴) / 𝑧]𝜑 ↔ [(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑)) | 
| 16 |  | 2fveq3 6911 | . . . 4
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → (1st
‘(1st ‘𝐴)) = (1st ‘(1st
‘〈𝑥, 𝑦, 𝑧〉))) | 
| 17 |  | ot1stg 8028 | . . . . 5
⊢ ((𝑥 ∈ V ∧ 𝑦 ∈ V ∧ 𝑧 ∈ V) →
(1st ‘(1st ‘〈𝑥, 𝑦, 𝑧〉)) = 𝑥) | 
| 18 | 8, 9, 10, 17 | mp3an 1463 | . . . 4
⊢
(1st ‘(1st ‘〈𝑥, 𝑦, 𝑧〉)) = 𝑥 | 
| 19 | 16, 18 | eqtr2di 2794 | . . 3
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → 𝑥 = (1st ‘(1st
‘𝐴))) | 
| 20 |  | sbceq1a 3799 | . . 3
⊢ (𝑥 = (1st
‘(1st ‘𝐴)) → ([(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑 ↔ [(1st
‘(1st ‘𝐴)) / 𝑥][(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑)) | 
| 21 | 19, 20 | syl 17 | . 2
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → ([(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑 ↔ [(1st
‘(1st ‘𝐴)) / 𝑥][(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑)) | 
| 22 | 6, 15, 21 | 3bitrrd 306 | 1
⊢ (𝐴 = 〈𝑥, 𝑦, 𝑧〉 → ([(1st
‘(1st ‘𝐴)) / 𝑥][(2nd
‘(1st ‘𝐴)) / 𝑦][(2nd ‘𝐴) / 𝑧]𝜑 ↔ 𝜑)) |