Proof of Theorem 3impexpbicom
Step | Hyp | Ref
| Expression |
1 | | bicom 221 |
. . . 4
⊢ ((𝜃 ↔ 𝜏) ↔ (𝜏 ↔ 𝜃)) |
2 | | imbi2 349 |
. . . . 5
⊢ (((𝜃 ↔ 𝜏) ↔ (𝜏 ↔ 𝜃)) → (((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜃 ↔ 𝜏)) ↔ ((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜏 ↔ 𝜃)))) |
3 | 2 | biimpcd 248 |
. . . 4
⊢ (((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜃 ↔ 𝜏)) → (((𝜃 ↔ 𝜏) ↔ (𝜏 ↔ 𝜃)) → ((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜏 ↔ 𝜃)))) |
4 | 1, 3 | mpi 20 |
. . 3
⊢ (((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜃 ↔ 𝜏)) → ((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜏 ↔ 𝜃))) |
5 | 4 | 3expd 1352 |
. 2
⊢ (((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜃 ↔ 𝜏)) → (𝜑 → (𝜓 → (𝜒 → (𝜏 ↔ 𝜃))))) |
6 | | 3impexp 1357 |
. . . 4
⊢ (((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜏 ↔ 𝜃)) ↔ (𝜑 → (𝜓 → (𝜒 → (𝜏 ↔ 𝜃))))) |
7 | 6 | biimpri 227 |
. . 3
⊢ ((𝜑 → (𝜓 → (𝜒 → (𝜏 ↔ 𝜃)))) → ((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜏 ↔ 𝜃))) |
8 | 7, 1 | syl6ibr 251 |
. 2
⊢ ((𝜑 → (𝜓 → (𝜒 → (𝜏 ↔ 𝜃)))) → ((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜃 ↔ 𝜏))) |
9 | 5, 8 | impbii 208 |
1
⊢ (((𝜑 ∧ 𝜓 ∧ 𝜒) → (𝜃 ↔ 𝜏)) ↔ (𝜑 → (𝜓 → (𝜒 → (𝜏 ↔ 𝜃))))) |