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Metamath Proof Explorer

Theorem pm4.64

Description: Theorem *4.64 of WhiteheadRussell p. 120. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm4.64 ⊢ ¬ φ → ψ ↔ φ ∨ ψ

Proof

Step Hyp Ref Expression
1 df-or ⊢ φ ∨ ψ ↔ ¬ φ → ψ
2 1 bicomi ⊢ ¬ φ → ψ ↔ φ ∨ ψ