Theorem necon4bbiddc 2279

Description: Contrapositive law deduction for inequality. (Contributed by Jim Kingdon, 19-May-2018.)

Hypothesis

Ref	Expression
necon4bbiddc.1	|- ( ph -> (DECID ps -> (DECID A = B -> ( -. ps <-> A =/= B ) ) ) )

Assertion

Ref	Expression
necon4bbiddc	|- ( ph -> (DECID ps -> (DECID A = B -> ( ps <-> A = B ) ) ) )

Proof of Theorem necon4bbiddc

Step	Hyp	Ref	Expression
1		necon4bbiddc.1	. . . . . 6 |- ( ph -> (DECID ps -> (DECID A = B -> ( -. ps <-> A =/= B ) ) ) )
2		bicom 128	. . . . . 6 |- ( ( -. ps <-> A =/= B ) <-> ( A =/= B <-> -. ps ) )
3	1, 2	syl8ib 155	. . . . 5 |- ( ph -> (DECID ps -> (DECID A = B -> ( A =/= B <-> -. ps ) ) ) )
4	3	com23 72	. . . 4 |- ( ph -> (DECID A = B -> (DECID ps -> ( A =/= B <-> -. ps ) ) ) )
5	4	necon4abiddc 2278	. . 3 |- ( ph -> (DECID A = B -> (DECID ps -> ( A = B <-> ps ) ) ) )
6	5	com23 72	. 2 |- ( ph -> (DECID ps -> (DECID A = B -> ( A = B <-> ps ) ) ) )
7		bicom 128	. 2 |- ( ( A = B <-> ps ) <-> ( ps <-> A = B ) )
8	6, 7	syl8ib 155	1 |- ( ph -> (DECID ps -> (DECID A = B -> ( ps <-> A = B ) ) ) )

Syntax hints:   -. wn 3   -> wi 4   <-> wb 98  DECID wdc 742   = wceq 1243   =/= wne 2204

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-in2 545  ax-io 630

This theorem depends on definitions:  df-bi 110  df-dc 743  df-ne 2206

This theorem is referenced by: (None)