Proof of Theorem orbi1rVD
Step | Hyp | Ref
| Expression |
1 | | idn1 42194 |
. . . . . 6
⊢ ( (𝜑 ↔ 𝜓) ▶ (𝜑 ↔ 𝜓) ) |
2 | | idn2 42233 |
. . . . . . 7
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜒 ∨ 𝜑) ) |
3 | | pm1.4 866 |
. . . . . . 7
⊢ ((𝜒 ∨ 𝜑) → (𝜑 ∨ 𝜒)) |
4 | 2, 3 | e2 42251 |
. . . . . 6
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜑 ∨ 𝜒) ) |
5 | | orbi1 915 |
. . . . . . 7
⊢ ((𝜑 ↔ 𝜓) → ((𝜑 ∨ 𝜒) ↔ (𝜓 ∨ 𝜒))) |
6 | 5 | biimpd 228 |
. . . . . 6
⊢ ((𝜑 ↔ 𝜓) → ((𝜑 ∨ 𝜒) → (𝜓 ∨ 𝜒))) |
7 | 1, 4, 6 | e12 42344 |
. . . . 5
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜓 ∨ 𝜒) ) |
8 | | pm1.4 866 |
. . . . 5
⊢ ((𝜓 ∨ 𝜒) → (𝜒 ∨ 𝜓)) |
9 | 7, 8 | e2 42251 |
. . . 4
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜑) ▶ (𝜒 ∨ 𝜓) ) |
10 | 9 | in2 42225 |
. . 3
⊢ ( (𝜑 ↔ 𝜓) ▶ ((𝜒 ∨ 𝜑) → (𝜒 ∨ 𝜓)) ) |
11 | | idn2 42233 |
. . . . . . 7
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜒 ∨ 𝜓) ) |
12 | | pm1.4 866 |
. . . . . . 7
⊢ ((𝜒 ∨ 𝜓) → (𝜓 ∨ 𝜒)) |
13 | 11, 12 | e2 42251 |
. . . . . 6
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜓 ∨ 𝜒) ) |
14 | 5 | biimprd 247 |
. . . . . 6
⊢ ((𝜑 ↔ 𝜓) → ((𝜓 ∨ 𝜒) → (𝜑 ∨ 𝜒))) |
15 | 1, 13, 14 | e12 42344 |
. . . . 5
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜑 ∨ 𝜒) ) |
16 | | pm1.4 866 |
. . . . 5
⊢ ((𝜑 ∨ 𝜒) → (𝜒 ∨ 𝜑)) |
17 | 15, 16 | e2 42251 |
. . . 4
⊢ ( (𝜑 ↔ 𝜓) , (𝜒 ∨ 𝜓) ▶ (𝜒 ∨ 𝜑) ) |
18 | 17 | in2 42225 |
. . 3
⊢ ( (𝜑 ↔ 𝜓) ▶ ((𝜒 ∨ 𝜓) → (𝜒 ∨ 𝜑)) ) |
19 | | impbi 207 |
. . 3
⊢ (((𝜒 ∨ 𝜑) → (𝜒 ∨ 𝜓)) → (((𝜒 ∨ 𝜓) → (𝜒 ∨ 𝜑)) → ((𝜒 ∨ 𝜑) ↔ (𝜒 ∨ 𝜓)))) |
20 | 10, 18, 19 | e11 42308 |
. 2
⊢ ( (𝜑 ↔ 𝜓) ▶ ((𝜒 ∨ 𝜑) ↔ (𝜒 ∨ 𝜓)) ) |
21 | 20 | in1 42191 |
1
⊢ ((𝜑 ↔ 𝜓) → ((𝜒 ∨ 𝜑) ↔ (𝜒 ∨ 𝜓))) |