Theorem pm2.3 775

Description: Theorem *2.3 of [WhiteheadRussell] p. 104. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.3	⊢ ((𝜑 ∨ (𝜓 ∨ 𝜒)) → (𝜑 ∨ (𝜒 ∨ 𝜓)))

Proof of Theorem pm2.3

Step	Hyp	Ref	Expression
1		pm1.4 727	. 2 ⊢ ((𝜓 ∨ 𝜒) → (𝜒 ∨ 𝜓))
2	1	orim2i 761	1 ⊢ ((𝜑 ∨ (𝜓 ∨ 𝜒)) → (𝜑 ∨ (𝜒 ∨ 𝜓)))

Syntax hints:   → wi 4   ∨ wo 708

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 709

This theorem depends on definitions:  df-bi 117

This theorem is referenced by: (None)