Theorem pm2.3 555

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		pm1.4 375	. 2 ⊢ ((ψ ∨ χ) → (χ ∨ ψ))
2	1	orim2i 504	1 ⊢ ((φ ∨ (ψ ∨ χ)) → (φ ∨ (χ ∨ ψ)))

Syntax hints:   → wi 4   ∨ wo 357

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 177  df-or 359

This theorem is referenced by: (None)