Theorem pm4.62

Description: Theorem *4.62 of WhiteheadRussell p. 120. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	pm4.62	⊢ ( ( 𝜑 → ¬ 𝜓 ) ↔ ( ¬ 𝜑 ∨ ¬ 𝜓 ) )

Proof

Step	Hyp	Ref	Expression
1		imor	⊢ ( ( 𝜑 → ¬ 𝜓 ) ↔ ( ¬ 𝜑 ∨ ¬ 𝜓 ) )