Metamath Proof Explorer


Theorem nanan

Description: Conjunction in terms of alternative denial. (Contributed by Mario Carneiro, 9-May-2015)

Ref Expression
Assertion nanan φ ψ ¬ φ ψ

Proof

Step Hyp Ref Expression
1 df-nan φ ψ ¬ φ ψ
2 1 con2bii φ ψ ¬ φ ψ