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Metamath Proof Explorer

Theorem pm2.47

Description: Theorem *2.47 of WhiteheadRussell p. 107. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.47 ( ¬ ( 𝜑 ∨ 𝜓 ) → ( ¬ 𝜑 ∨ 𝜓 ) )

Proof

Step Hyp Ref Expression
1 pm2.45 ⊢ ( ¬ ( 𝜑 ∨ 𝜓 ) → ¬ 𝜑 )
2 1 orcd ⊢ ( ¬ ( 𝜑 ∨ 𝜓 ) → ( ¬ 𝜑 ∨ 𝜓 ) )