Theorem pm2.38

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

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

Proof

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