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Theorem frege55aid 41433
Description: Lemma for frege57aid 41440. Core proof of Proposition 55 of [Frege1879] p. 50. (Contributed by RP, 24-Dec-2019.)
Assertion
Ref Expression
frege55aid ((𝜑𝜓) → (𝜓𝜑))

Proof of Theorem frege55aid
StepHypRef Expression
1 bicom1 220 1 ((𝜑𝜓) → (𝜓𝜑))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 205
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 206
This theorem is referenced by:  frege56aid  41438
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