Theorem dn1 1055

Description: A single axiom for Boolean algebra known as DN₁. See McCune, Veroff, Fitelson, Harris, Feist, Wos, Short single axioms for Boolean algebra, Journal of Automated Reasoning, 29(1):1--16, 2002. (https://www.cs.unm.edu/~mccune/papers/basax/v12.pdf). (Contributed by Jeff Hankins, 3-Jul-2009.) (Proof shortened by Andrew Salmon, 13-May-2011.) (Proof shortened by Wolf Lammen, 6-Jan-2013.)

Assertion

Ref	Expression
dn1	⊢ (¬ (¬ (¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∨ ¬ (𝜑 ∨ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))) ↔ 𝜒)

Proof of Theorem dn1

Step	Hyp	Ref	Expression
1		pm2.45 879	. . . . 5 ⊢ (¬ (𝜑 ∨ 𝜓) → ¬ 𝜑)
2		imnan 400	. . . . 5 ⊢ ((¬ (𝜑 ∨ 𝜓) → ¬ 𝜑) ↔ ¬ (¬ (𝜑 ∨ 𝜓) ∧ 𝜑))
3	1, 2	mpbi 229	. . . 4 ⊢ ¬ (¬ (𝜑 ∨ 𝜓) ∧ 𝜑)
4	3	biorfi 936	. . 3 ⊢ (𝜒 ↔ (𝜒 ∨ (¬ (𝜑 ∨ 𝜓) ∧ 𝜑)))
5		orcom 867	. . 3 ⊢ ((𝜒 ∨ (¬ (𝜑 ∨ 𝜓) ∧ 𝜑)) ↔ ((¬ (𝜑 ∨ 𝜓) ∧ 𝜑) ∨ 𝜒))
6		ordir 1004	. . 3 ⊢ (((¬ (𝜑 ∨ 𝜓) ∧ 𝜑) ∨ 𝜒) ↔ ((¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∧ (𝜑 ∨ 𝜒)))
7	4, 5, 6	3bitri 297	. 2 ⊢ (𝜒 ↔ ((¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∧ (𝜑 ∨ 𝜒)))
8		pm4.45 995	. . . . 5 ⊢ (𝜒 ↔ (𝜒 ∧ (𝜒 ∨ 𝜃)))
9		anor 980	. . . . 5 ⊢ ((𝜒 ∧ (𝜒 ∨ 𝜃)) ↔ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))
10	8, 9	bitri 274	. . . 4 ⊢ (𝜒 ↔ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))
11	10	orbi2i 910	. . 3 ⊢ ((𝜑 ∨ 𝜒) ↔ (𝜑 ∨ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃))))
12	11	anbi2i 623	. 2 ⊢ (((¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∧ (𝜑 ∨ 𝜒)) ↔ ((¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∧ (𝜑 ∨ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))))
13		anor 980	. 2 ⊢ (((¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∧ (𝜑 ∨ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))) ↔ ¬ (¬ (¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∨ ¬ (𝜑 ∨ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))))
14	7, 12, 13	3bitrri 298	1 ⊢ (¬ (¬ (¬ (𝜑 ∨ 𝜓) ∨ 𝜒) ∨ ¬ (𝜑 ∨ ¬ (¬ 𝜒 ∨ ¬ (𝜒 ∨ 𝜃)))) ↔ 𝜒)

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 205   ∧ wa 396   ∨ wo 844

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 206  df-an 397  df-or 845

This theorem is referenced by: (None)