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Theorem dfrex2 2627
Description: Relationship between restricted universal and existential quantifiers. (Contributed by NM, 21-Jan-1997.)
Assertion
Ref Expression
dfrex2 (x A φ ↔ ¬ x A ¬ φ)

Proof of Theorem dfrex2
StepHypRef Expression
1 ralnex 2624 . 2 (x A ¬ φ ↔ ¬ x A φ)
21con2bii 322 1 (x A φ ↔ ¬ x A ¬ φ)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wb 176  wral 2614  wrex 2615
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557
This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1542  df-ral 2619  df-rex 2620
This theorem is referenced by:  nfrexd  2666  nfrex  2669  rexim  2718  r19.30  2756  r19.35  2758  cbvrexf  2830  rspcimedv  2957  sbcrext  3119  cbvrexcsf  3199  r19.9rzv  3644  rexiunxp  4824  rexxpf  4828  disjex  5823  nnc3n3p1  6278
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