Metamath Proof Explorer


Theorem notbinot2

Description: Commutation rule between negation and biconditional. (Contributed by Giovanni Mascellani, 15-Sep-2017)

Ref Expression
Assertion notbinot2 ¬ φ ψ ¬ φ ψ

Proof

Step Hyp Ref Expression
1 nbbn ¬ φ ψ ¬ φ ψ
2 1 bicomi ¬ φ ψ ¬ φ ψ