Theorem pm5.75OLD 979

Description: Obsolete proof of pm5.75 978 as of 12-Feb-2021. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Andrew Salmon, 7-May-2011.) (Proof shortened by Wolf Lammen, 23-Dec-2012.) (New usage is discouraged.) (Proof modification is discouraged.)

Assertion

Ref	Expression
pm5.75OLD	|- ( ( ( ch -> -. ps ) /\ ( ph <-> ( ps \/ ch ) ) ) -> ( ( ph /\ -. ps ) <-> ch ) )

Proof of Theorem pm5.75OLD

Step	Hyp	Ref	Expression
1		anbi1 743	. . 3 |- ( ( ph <-> ( ps \/ ch ) ) -> ( ( ph /\ -. ps ) <-> ( ( ps \/ ch ) /\ -. ps ) ) )
2		orcom 402	. . . . 5 |- ( ( ps \/ ch ) <-> ( ch \/ ps ) )
3	2	anbi1i 731	. . . 4 |- ( ( ( ps \/ ch ) /\ -. ps ) <-> ( ( ch \/ ps ) /\ -. ps ) )
4		pm5.61 749	. . . 4 |- ( ( ( ch \/ ps ) /\ -. ps ) <-> ( ch /\ -. ps ) )
5	3, 4	bitri 264	. . 3 |- ( ( ( ps \/ ch ) /\ -. ps ) <-> ( ch /\ -. ps ) )
6	1, 5	syl6bb 276	. 2 |- ( ( ph <-> ( ps \/ ch ) ) -> ( ( ph /\ -. ps ) <-> ( ch /\ -. ps ) ) )
7		pm4.71 662	. . . 4 |- ( ( ch -> -. ps ) <-> ( ch <-> ( ch /\ -. ps ) ) )
8	7	biimpi 206	. . 3 |- ( ( ch -> -. ps ) -> ( ch <-> ( ch /\ -. ps ) ) )
9	8	bicomd 213	. 2 |- ( ( ch -> -. ps ) -> ( ( ch /\ -. ps ) <-> ch ) )
10	6, 9	sylan9bbr 737	1 |- ( ( ( ch -> -. ps ) /\ ( ph <-> ( ps \/ ch ) ) ) -> ( ( ph /\ -. ps ) <-> ch ) )

Syntax hints:   -. wn 3   -> wi 4   <-> wb 196   \/ wo 383   /\ wa 384

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386

This theorem is referenced by: (None)