Metamath Proof Explorer


Theorem bi13imp2

Description: Similar to 3imp except the outermost and innermost implications are biconditionals. (Contributed by Alan Sare, 6-Nov-2017)

Ref Expression
Hypothesis bi13imp2.1 φ ψ χ θ
Assertion bi13imp2 φ ψ χ θ

Proof

Step Hyp Ref Expression
1 bi13imp2.1 φ ψ χ θ
2 1 biimpi φ ψ χ θ
3 2 bi33imp12 φ ψ χ θ