Proof of Theorem orbi1rVD
| Step | Hyp | Ref
| Expression |
| 1 | | idn1 44594 |
. . . . . 6
⊢ ( (𝜑 ↔ 𝜓) ▶ (𝜑 ↔ 𝜓) ) |
| 2 | | idn2 44633 |
. . . . . . 7
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜒 ∨ 𝜑) ) |
| 3 | | pm1.4 870 |
. . . . . . 7
⊢ ((𝜒 ∨ 𝜑) → (𝜑 ∨ 𝜒)) |
| 4 | 2, 3 | e2 44651 |
. . . . . 6
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜑 ∨ 𝜒) ) |
| 5 | | orbi1 918 |
. . . . . . 7
⊢ ((𝜑 ↔ 𝜓) → ((𝜑 ∨ 𝜒) ↔ (𝜓 ∨ 𝜒))) |
| 6 | 5 | biimpd 229 |
. . . . . 6
⊢ ((𝜑 ↔ 𝜓) → ((𝜑 ∨ 𝜒) → (𝜓 ∨ 𝜒))) |
| 7 | 1, 4, 6 | e12 44744 |
. . . . 5
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜓 ∨ 𝜒) ) |
| 8 | | pm1.4 870 |
. . . . 5
⊢ ((𝜓 ∨ 𝜒) → (𝜒 ∨ 𝜓)) |
| 9 | 7, 8 | e2 44651 |
. . . 4
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜒 ∨ 𝜓) ) |
| 10 | 9 | in2 44625 |
. . 3
⊢ ( (𝜑 ↔ 𝜓) ▶ ((𝜒 ∨ 𝜑) → (𝜒 ∨ 𝜓)) ) |
| 11 | | idn2 44633 |
. . . . . . 7
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜒 ∨ 𝜓) ) |
| 12 | | pm1.4 870 |
. . . . . . 7
⊢ ((𝜒 ∨ 𝜓) → (𝜓 ∨ 𝜒)) |
| 13 | 11, 12 | e2 44651 |
. . . . . 6
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜓 ∨ 𝜒) ) |
| 14 | 5 | biimprd 248 |
. . . . . 6
⊢ ((𝜑 ↔ 𝜓) → ((𝜓 ∨ 𝜒) → (𝜑 ∨ 𝜒))) |
| 15 | 1, 13, 14 | e12 44744 |
. . . . 5
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜑 ∨ 𝜒) ) |
| 16 | | pm1.4 870 |
. . . . 5
⊢ ((𝜑 ∨ 𝜒) → (𝜒 ∨ 𝜑)) |
| 17 | 15, 16 | e2 44651 |
. . . 4
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜒 ∨ 𝜑) ) |
| 18 | 17 | in2 44625 |
. . 3
⊢ ( (𝜑 ↔ 𝜓) ▶ ((𝜒 ∨ 𝜓) → (𝜒 ∨ 𝜑)) ) |
| 19 | | impbi 208 |
. . 3
⊢ (((𝜒 ∨ 𝜑) → (𝜒 ∨ 𝜓)) → (((𝜒 ∨ 𝜓) → (𝜒 ∨ 𝜑)) → ((𝜒 ∨ 𝜑) ↔ (𝜒 ∨ 𝜓)))) |
| 20 | 10, 18, 19 | e11 44708 |
. 2
⊢ ( (𝜑 ↔ 𝜓) ▶ ((𝜒 ∨ 𝜑) ↔ (𝜒 ∨ 𝜓)) ) |
| 21 | 20 | in1 44591 |
1
⊢ ((𝜑 ↔ 𝜓) → ((𝜒 ∨ 𝜑) ↔ (𝜒 ∨ 𝜓))) |