Theorem necon2bbiidc 2401

Description: Contrapositive inference for inequality. (Contributed by Jim Kingdon, 16-May-2018.)

Hypothesis

Ref	Expression
necon2bbii.1	|- (DECID A = B -> ( ph <-> A =/= B ) )

Assertion

Ref	Expression
necon2bbiidc	|- (DECID A = B -> ( A = B <-> -. ph ) )

Proof of Theorem necon2bbiidc

Step	Hyp	Ref	Expression
1		necon2bbii.1	. . . 4 |- (DECID A = B -> ( ph <-> A =/= B ) )
2	1	bicomd 140	. . 3 |- (DECID A = B -> ( A =/= B <-> ph ) )
3	2	necon1bbiidc 2397	. 2 |- (DECID A = B -> ( -. ph <-> A = B ) )
4	3	bicomd 140	1 |- (DECID A = B -> ( A = B <-> -. ph ) )

Syntax hints:   -. wn 3   -> wi 4   <-> wb 104  DECID wdc 824   = wceq 1343   =/= wne 2336

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-in1 604  ax-in2 605  ax-io 699

This theorem depends on definitions:  df-bi 116  df-dc 825  df-ne 2337

This theorem is referenced by: (None)