Proof of Theorem an6
| Step | Hyp | Ref
| Expression |
| 1 | | df-3an 781 |
. . . 4
⊢ ((φ ⋀ ψ ⋀ χ) ↔ ((φ ⋀ ψ) ⋀ χ)) |
| 2 | | df-3an 781 |
. . . 4
⊢ ((θ ⋀
τ ⋀
η) ↔ ((θ ⋀
τ) ⋀
η)) |
| 3 | 1, 2 | anbi12i 485 |
. . 3
⊢ (((φ ⋀ ψ ⋀ χ) ⋀
(θ ⋀ τ ⋀ η))
↔ (((φ ⋀ ψ) ⋀ χ) ⋀ ((θ
⋀ τ)
⋀ η))) |
| 4 | | an4 509 |
. . 3
⊢ ((((φ ⋀ ψ) ⋀ χ) ⋀
((θ ⋀ τ) ⋀ η))
↔ (((φ ⋀ ψ) ⋀ (θ
⋀ τ)) ⋀
(χ ⋀
η))) |
| 5 | | an4 509 |
. . . 4
⊢ (((φ ⋀ ψ) ⋀
(θ ⋀ τ))
↔ ((φ ⋀ θ)
⋀ (ψ
⋀ τ))) |
| 6 | 5 | anbi1i 484 |
. . 3
⊢ ((((φ ⋀ ψ) ⋀
(θ ⋀ τ))
⋀ (χ
⋀ η)) ↔ (((φ ⋀ θ) ⋀
(ψ ⋀
τ)) ⋀ (χ ⋀ η))) |
| 7 | 3, 4, 6 | 3bitri 177 |
. 2
⊢ (((φ ⋀ ψ ⋀ χ) ⋀
(θ ⋀ τ ⋀ η))
↔ (((φ ⋀ θ)
⋀ (ψ
⋀ τ)) ⋀
(χ ⋀
η))) |
| 8 | | df-3an 781 |
. 2
⊢ (((φ ⋀ θ) ⋀
(ψ ⋀
τ) ⋀
(χ ⋀
η)) ↔ (((φ ⋀ θ) ⋀
(ψ ⋀
τ)) ⋀ (χ ⋀ η))) |
| 9 | 7, 8 | bitr4i 176 |
1
⊢ (((φ ⋀ ψ ⋀ χ) ⋀
(θ ⋀ τ ⋀ η))
↔ ((φ ⋀ θ)
⋀ (ψ
⋀ τ)
⋀ (χ
⋀ η))) |