Theorem pm2.38 815

Description: Theorem *2.38 of [WhiteheadRussell] p. 105. (Contributed by NM, 6-Mar-2008.)

Assertion

Ref	Expression
pm2.38	⊢ ((ψ → χ) → ((ψ ∨ φ) → (χ ∨ φ)))

Proof of Theorem pm2.38

Step	Hyp	Ref	Expression
1		id 19	. 2 ⊢ ((ψ → χ) → (ψ → χ))
2	1	orim1d 812	1 ⊢ ((ψ → χ) → ((ψ ∨ φ) → (χ ∨ φ)))

This proof depends on syntax axioms:   → wi 4   ∨ wo 357

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 177  df-or 359  df-an 360

This theorem is used by:  pm2.36  816  pm2.37  817