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Theorem imbi2 314
Description: Theorem *4.85 of [WhiteheadRussell] p. 122. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 19-May-2013.)
Assertion
Ref Expression
imbi2 ((φψ) → ((χφ) ↔ (χψ)))

Proof of Theorem imbi2
StepHypRef Expression
1 id 19 . 2 ((φψ) → (φψ))
21imbi2d 307 1 ((φψ) → ((χφ) ↔ (χψ)))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 176
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 177
This theorem is referenced by:  3impexpbicom  1367
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