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Theorem pm5.5 240
Description: Theorem *5.5 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm5.5 (𝜑 → ((𝜑𝜓) ↔ 𝜓))

Proof of Theorem pm5.5
StepHypRef Expression
1 biimt 239 . 2 (𝜑 → (𝜓 ↔ (𝜑𝜓)))
21bicomd 139 1 (𝜑 → ((𝜑𝜓) ↔ 𝜓))
Colors of variables: wff set class
Syntax hints:  wi 4  wb 103
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106
This theorem depends on definitions:  df-bi 115
This theorem is referenced by:  imim21b  250  elabgt  2757  sbceqal  2894  dffun8  5043  ordiso2  6726  indstr2  9094  dfgcd2  11277
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