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Metamath Proof Explorer

Theorem pm3.12

Description: Theorem *3.12 of WhiteheadRussell p. 111. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm3.12 ⊢ ¬ φ ∨ ¬ ψ ∨ φ ∧ ψ

Proof

Step Hyp Ref Expression
1 pm3.11 ⊢ ¬ ¬ φ ∨ ¬ ψ → φ ∧ ψ
2 1 orri ⊢ ¬ φ ∨ ¬ ψ ∨ φ ∧ ψ