Step | Hyp | Ref
| Expression |
1 | | eleq1 2822 |
. . . 4
⊢ (𝐴 = 𝐵 → (𝐴 ∈ V ↔ 𝐵 ∈ V)) |
2 | 1 | anbi1d 631 |
. . 3
⊢ (𝐴 = 𝐵 → ((𝐴 ∈ V ∧ 𝐶 ∈ V) ↔ (𝐵 ∈ V ∧ 𝐶 ∈ V))) |
3 | | sneq 4638 |
. . . 4
⊢ (𝐴 = 𝐵 → {𝐴} = {𝐵}) |
4 | | preq1 4737 |
. . . 4
⊢ (𝐴 = 𝐵 → {𝐴, 𝐶} = {𝐵, 𝐶}) |
5 | 3, 4 | preq12d 4745 |
. . 3
⊢ (𝐴 = 𝐵 → {{𝐴}, {𝐴, 𝐶}} = {{𝐵}, {𝐵, 𝐶}}) |
6 | 2, 5 | ifbieq1d 4552 |
. 2
⊢ (𝐴 = 𝐵 → if((𝐴 ∈ V ∧ 𝐶 ∈ V), {{𝐴}, {𝐴, 𝐶}}, ∅) = if((𝐵 ∈ V ∧ 𝐶 ∈ V), {{𝐵}, {𝐵, 𝐶}}, ∅)) |
7 | | dfopif 4870 |
. 2
⊢
⟨𝐴, 𝐶⟩ = if((𝐴 ∈ V ∧ 𝐶 ∈ V), {{𝐴}, {𝐴, 𝐶}}, ∅) |
8 | | dfopif 4870 |
. 2
⊢
⟨𝐵, 𝐶⟩ = if((𝐵 ∈ V ∧ 𝐶 ∈ V), {{𝐵}, {𝐵, 𝐶}}, ∅) |
9 | 6, 7, 8 | 3eqtr4g 2798 |
1
⊢ (𝐴 = 𝐵 → ⟨𝐴, 𝐶⟩ = ⟨𝐵, 𝐶⟩) |