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Metamath Proof Explorer

Theorem pm2.1

Description: Theorem *2.1 of WhiteheadRussell p. 101. (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 23-Nov-2012)

Ref Expression
Assertion pm2.1 ( ¬ 𝜑 ∨ 𝜑 )

Proof

Step Hyp Ref Expression
1 id ⊢ ( 𝜑 → 𝜑 )
2 1 imori ⊢ ( ¬ 𝜑 ∨ 𝜑 )