Metamath Proof Explorer


Theorem nan

Description: Theorem to move a conjunct in and out of a negation. (Contributed by NM, 9-Nov-2003)

Ref Expression
Assertion nan ( ( 𝜑 → ¬ ( 𝜓𝜒 ) ) ↔ ( ( 𝜑𝜓 ) → ¬ 𝜒 ) )

Proof

Step Hyp Ref Expression
1 impexp ( ( ( 𝜑𝜓 ) → ¬ 𝜒 ) ↔ ( 𝜑 → ( 𝜓 → ¬ 𝜒 ) ) )
2 imnan ( ( 𝜓 → ¬ 𝜒 ) ↔ ¬ ( 𝜓𝜒 ) )
3 2 imbi2i ( ( 𝜑 → ( 𝜓 → ¬ 𝜒 ) ) ↔ ( 𝜑 → ¬ ( 𝜓𝜒 ) ) )
4 1 3 bitr2i ( ( 𝜑 → ¬ ( 𝜓𝜒 ) ) ↔ ( ( 𝜑𝜓 ) → ¬ 𝜒 ) )