Theorem dedlema 959

Description: Lemma for iftrue 3525. (Contributed by NM, 26-Jun-2002.) (Proof shortened by Andrew Salmon, 7-May-2011.)

Assertion

Ref	Expression
dedlema	|- ( ph -> ( ps <-> ( ( ps /\ ph ) \/ ( ch /\ -. ph ) ) ) )

Proof of Theorem dedlema

Step	Hyp	Ref	Expression
1		orc 702	. . 3 |- ( ( ps /\ ph ) -> ( ( ps /\ ph ) \/ ( ch /\ -. ph ) ) )
2	1	expcom 115	. 2 |- ( ph -> ( ps -> ( ( ps /\ ph ) \/ ( ch /\ -. ph ) ) ) )
3		simpl 108	. . . 4 |- ( ( ps /\ ph ) -> ps )
4	3	a1i 9	. . 3 |- ( ph -> ( ( ps /\ ph ) -> ps ) )
5		pm2.24 611	. . . 4 |- ( ph -> ( -. ph -> ps ) )
6	5	adantld 276	. . 3 |- ( ph -> ( ( ch /\ -. ph ) -> ps ) )
7	4, 6	jaod 707	. 2 |- ( ph -> ( ( ( ps /\ ph ) \/ ( ch /\ -. ph ) ) -> ps ) )
8	2, 7	impbid 128	1 |- ( ph -> ( ps <-> ( ( ps /\ ph ) \/ ( ch /\ -. ph ) ) ) )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 103   <-> wb 104   \/ wo 698

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in2 605  ax-io 699

This theorem depends on definitions:  df-bi 116

This theorem is referenced by:  iftrue  3525