Theorem pm2.45

Description: Theorem *2.45 of WhiteheadRussell p. 106. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm2.45	⊢ ( ¬ ( 𝜑 ∨ 𝜓 ) → ¬ 𝜑 )

Proof

Step	Hyp	Ref	Expression
1		orc	⊢ ( 𝜑 → ( 𝜑 ∨ 𝜓 ) )
2	1	con3i	⊢ ( ¬ ( 𝜑 ∨ 𝜓 ) → ¬ 𝜑 )