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Axiom ax-in1 554
Description: 'Not' introduction. One of the axioms of propositional logic. (Contributed by Mario Carneiro, 31-Jan-2015.)
Assertion
Ref Expression
ax-in1  |-  ( (
ph  ->  -.  ph )  ->  -.  ph )

Detailed syntax breakdown of Axiom ax-in1
StepHypRef Expression
1 wph . . 3  wff  ph
21wn 3 . . 3  wff  -.  ph
31, 2wi 4 . 2  wff  ( ph  ->  -.  ph )
43, 2wi 4 1  wff  ( (
ph  ->  -.  ph )  ->  -.  ph )
Colors of variables: wff set class
This axiom is referenced by:  pm2.01  556
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