Theorem pm2.82 977

Description: Theorem *2.82 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.82	⊢ (((𝜑 ∨ 𝜓) ∨ 𝜒) → (((𝜑 ∨ ¬ 𝜒) ∨ 𝜃) → ((𝜑 ∨ 𝜓) ∨ 𝜃)))

Proof of Theorem pm2.82

Step	Hyp	Ref	Expression
1		pm2.24 124	. . . 4 ⊢ (𝜒 → (¬ 𝜒 → 𝜓))
2	1	orim2d 968	. . 3 ⊢ (𝜒 → ((𝜑 ∨ ¬ 𝜒) → (𝜑 ∨ 𝜓)))
3	2	jao1i 858	. 2 ⊢ (((𝜑 ∨ 𝜓) ∨ 𝜒) → ((𝜑 ∨ ¬ 𝜒) → (𝜑 ∨ 𝜓)))
4	3	orim1d 967	1 ⊢ (((𝜑 ∨ 𝜓) ∨ 𝜒) → (((𝜑 ∨ ¬ 𝜒) ∨ 𝜃) → ((𝜑 ∨ 𝜓) ∨ 𝜃)))

Syntax hints:  ¬ wn 3   → wi 4   ∨ wo 847

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 207  df-an 396  df-or 848

This theorem is referenced by: (None)