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Theorem pm4.71 614
Description: Implication in terms of biconditional and conjunction. Theorem *4.71 of [WhiteheadRussell] p. 120. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 2-Dec-2012.)
Assertion
Ref Expression
pm4.71  |-  ( (
ph  ->  ps )  <->  ( ph  <->  (
ph  /\  ps )
) )

Proof of Theorem pm4.71
StepHypRef Expression
1 simpl 445 . . 3  |-  ( (
ph  /\  ps )  ->  ph )
21biantru 493 . 2  |-  ( (
ph  ->  ( ph  /\  ps ) )  <->  ( ( ph  ->  ( ph  /\  ps ) )  /\  (
( ph  /\  ps )  ->  ph ) ) )
3 anclb 532 . 2  |-  ( (
ph  ->  ps )  <->  ( ph  ->  ( ph  /\  ps ) ) )
4 dfbi2 612 . 2  |-  ( (
ph 
<->  ( ph  /\  ps ) )  <->  ( ( ph  ->  ( ph  /\  ps ) )  /\  (
( ph  /\  ps )  ->  ph ) ) )
52, 3, 43bitr4i 270 1  |-  ( (
ph  ->  ps )  <->  ( ph  <->  (
ph  /\  ps )
) )
Colors of variables: wff set class
Syntax hints:    -> wi 6    <-> wb 178    /\ wa 360
This theorem is referenced by:  pm4.71r  615  pm4.71i  616  pm4.71d  618  bigolden  906  pm5.75  908  exintrbi  1615  rabid2  2676  dfss2  3092  disj3  3406  dmopab3  4798
This theorem was proved from axioms:  ax-1 7  ax-2 8  ax-3 9  ax-mp 10
This theorem depends on definitions:  df-bi 179  df-an 362
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