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Theorem pm4.87 567
Description: Theorem *4.87 of [WhiteheadRussell] p. 122. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Eric Schmidt, 26-Oct-2006.)
Assertion
Ref Expression
pm4.87

Proof of Theorem pm4.87
StepHypRef Expression
1 impexp 433 . . 3
2 bi2.04 350 . . 3
31, 2pm3.2i 441 . 2
4 impexp 433 . . 3
54bicomi 193 . 2
63, 5pm3.2i 441 1
Colors of variables: wff setvar class
Syntax hints:   wi 4   wb 176   wa 358
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  df-an 360
This theorem is referenced by: (None)
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