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Theorem pm4.25 675
Description: Theorem *4.25 of [WhiteheadRussell] p. 117. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm4.25 (𝜑 ↔ (𝜑𝜑))

Proof of Theorem pm4.25
StepHypRef Expression
1 oridm 674 . 2 ((𝜑𝜑) ↔ 𝜑)
21bicomi 123 1 (𝜑 ↔ (𝜑𝜑))
Colors of variables: wff set class
Syntax hints:  wb 98  wo 629
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-io 630
This theorem depends on definitions:  df-bi 110
This theorem is referenced by: (None)
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