Metamath Proof Explorer


Theorem nfna1

Description: A convenience theorem particularly designed to remove dependencies on ax-11 in conjunction with distinctors. (Contributed by Wolf Lammen, 2-Sep-2018)

Ref Expression
Assertion nfna1 x¬xφ

Proof

Step Hyp Ref Expression
1 nfa1 xxφ
2 1 nfn x¬xφ