Proof of Theorem opeq2
| Step | Hyp | Ref
| Expression |
| 1 | | eleq1 2821 |
. . . 4
⊢ (𝐴 = 𝐵 → (𝐴 ∈ V ↔ 𝐵 ∈ V)) |
| 2 | 1 | anbi2d 630 |
. . 3
⊢ (𝐴 = 𝐵 → ((𝐶 ∈ V ∧ 𝐴 ∈ V) ↔ (𝐶 ∈ V ∧ 𝐵 ∈ V))) |
| 3 | | preq2 4716 |
. . . 4
⊢ (𝐴 = 𝐵 → {𝐶, 𝐴} = {𝐶, 𝐵}) |
| 4 | 3 | preq2d 4722 |
. . 3
⊢ (𝐴 = 𝐵 → {{𝐶}, {𝐶, 𝐴}} = {{𝐶}, {𝐶, 𝐵}}) |
| 5 | 2, 4 | ifbieq1d 4532 |
. 2
⊢ (𝐴 = 𝐵 → if((𝐶 ∈ V ∧ 𝐴 ∈ V), {{𝐶}, {𝐶, 𝐴}}, ∅) = if((𝐶 ∈ V ∧ 𝐵 ∈ V), {{𝐶}, {𝐶, 𝐵}}, ∅)) |
| 6 | | dfopif 4852 |
. 2
⊢
〈𝐶, 𝐴〉 = if((𝐶 ∈ V ∧ 𝐴 ∈ V), {{𝐶}, {𝐶, 𝐴}}, ∅) |
| 7 | | dfopif 4852 |
. 2
⊢
〈𝐶, 𝐵〉 = if((𝐶 ∈ V ∧ 𝐵 ∈ V), {{𝐶}, {𝐶, 𝐵}}, ∅) |
| 8 | 5, 6, 7 | 3eqtr4g 2794 |
1
⊢ (𝐴 = 𝐵 → 〈𝐶, 𝐴〉 = 〈𝐶, 𝐵〉) |