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Theorem pm2.521 164
Description: Theorem *2.521 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 8-Oct-2012.)
Assertion
Ref Expression
pm2.521 (¬ (𝜑𝜓) → (𝜓𝜑))

Proof of Theorem pm2.521
StepHypRef Expression
1 simplim 161 . 2 (¬ (𝜑𝜓) → 𝜑)
21a1d 25 1 (¬ (𝜑𝜓) → (𝜓𝜑))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  pm2.52  165  ifpimim  36697
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