Theorem nex 1487

Description: Generalization rule for negated wff. (Contributed by NM, 18-May-1994.)

Hypothesis

Ref	Expression
nex.1	|- -. ph

Assertion

Ref	Expression
nex	|- -. E. x ph

Proof of Theorem nex

Step	Hyp	Ref	Expression
1		alnex 1486	. 2 |- ( A. x -. ph <-> -. E. x ph )
2		nex.1	. 2 |- -. ph
3	1, 2	mpgbi 1439	1 |- -. E. x ph

Syntax hints:   -. wn 3   E.wex 1479

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 604  ax-in2 605  ax-5 1434  ax-gen 1436  ax-ie2 1481

This theorem depends on definitions:  df-bi 116  df-tru 1345  df-fal 1348

This theorem is referenced by:  ru  2945  0nelxp  4626  0xp  4678  dm0  4812  co02  5111  0fv  5515  mpo0  5903  0npr  7415