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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