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Theorem con2 571
Description: Contraposition. Theorem *2.03 of [WhiteheadRussell] p. 100. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 12-Feb-2013.)
Assertion
Ref Expression
con2 ((φ → ¬ ψ) → (ψ → ¬ φ))

Proof of Theorem con2
StepHypRef Expression
1 id 19 . 2 ((φ → ¬ ψ) → (φ → ¬ ψ))
21con2d 554 1 ((φ → ¬ ψ) → (ψ → ¬ φ))
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-in1 544  ax-in2 545
This theorem is referenced by:  con2b  592
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