Theorem necon1idc 2359

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

Hypothesis

Ref	Expression
necon1idc.1	|- ( A =/= B -> C = D )

Assertion

Ref	Expression
necon1idc	|- (DECID A = B -> ( C =/= D -> A = B ) )

Proof of Theorem necon1idc

Step	Hyp	Ref	Expression
1		df-ne 2307	. . . 4 |- ( A =/= B <-> -. A = B )
2		necon1idc.1	. . . 4 |- ( A =/= B -> C = D )
3	1, 2	sylbir 134	. . 3 |- ( -. A = B -> C = D )
4	3	a1i 9	. 2 |- (DECID A = B -> ( -. A = B -> C = D ) )
5	4	necon1aidc 2357	1 |- (DECID A = B -> ( C =/= D -> A = B ) )

Syntax hints:   -. wn 3   -> wi 4  DECID wdc 819   = wceq 1331   =/= wne 2306

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 603  ax-in2 604  ax-io 698

This theorem depends on definitions:  df-bi 116  df-stab 816  df-dc 820  df-ne 2307

This theorem is referenced by: (None)