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Theorem stabnot 775
Description: Every formula of the form ¬ 𝜑 is stable. Uses notnotnot 661. (Contributed by David A. Wheeler, 13-Aug-2018.)
Assertion
Ref Expression
stabnot STAB ¬ 𝜑

Proof of Theorem stabnot
StepHypRef Expression
1 notnotnot 661 . . 3 (¬ ¬ ¬ 𝜑 ↔ ¬ 𝜑)
21biimpi 118 . 2 (¬ ¬ ¬ 𝜑 → ¬ 𝜑)
3 df-stab 774 . 2 (STAB ¬ 𝜑 ↔ (¬ ¬ ¬ 𝜑 → ¬ 𝜑))
42, 3mpbir 144 1 STAB ¬ 𝜑
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4  STAB wstab 773
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in1 577  ax-in2 578
This theorem depends on definitions:  df-bi 115  df-stab 774
This theorem is referenced by: (None)
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