Metamath Proof Explorer


Theorem ifpdfbi

Description: Define the biconditional as conditional logic operator. (Contributed by RP, 20-Apr-2020) (Proof shortened by Wolf Lammen, 30-Apr-2024)

Ref Expression
Assertion ifpdfbi ( ( 𝜑𝜓 ) ↔ if- ( 𝜑 , 𝜓 , ¬ 𝜓 ) )

Proof

Step Hyp Ref Expression
1 con34b ( ( 𝜓𝜑 ) ↔ ( ¬ 𝜑 → ¬ 𝜓 ) )
2 1 anbi2i ( ( ( 𝜑𝜓 ) ∧ ( 𝜓𝜑 ) ) ↔ ( ( 𝜑𝜓 ) ∧ ( ¬ 𝜑 → ¬ 𝜓 ) ) )
3 dfbi2 ( ( 𝜑𝜓 ) ↔ ( ( 𝜑𝜓 ) ∧ ( 𝜓𝜑 ) ) )
4 dfifp2 ( if- ( 𝜑 , 𝜓 , ¬ 𝜓 ) ↔ ( ( 𝜑𝜓 ) ∧ ( ¬ 𝜑 → ¬ 𝜓 ) ) )
5 2 3 4 3bitr4i ( ( 𝜑𝜓 ) ↔ if- ( 𝜑 , 𝜓 , ¬ 𝜓 ) )