Metamath Proof Explorer


Theorem pm2.18dOLD

Description: Obsolete version of pm2.18d as of 17-Nov-2023. (Contributed by FL, 12-Jul-2009) (Proof shortened by Andrew Salmon, 7-May-2011) (Proof modification is discouraged.) (New usage is discouraged.)

Ref Expression
Hypothesis pm2.18dOLD.1 ( 𝜑 → ( ¬ 𝜓𝜓 ) )
Assertion pm2.18dOLD ( 𝜑𝜓 )

Proof

Step Hyp Ref Expression
1 pm2.18dOLD.1 ( 𝜑 → ( ¬ 𝜓𝜓 ) )
2 pm2.18OLD ( ( ¬ 𝜓𝜓 ) → 𝜓 )
3 1 2 syl ( 𝜑𝜓 )