Theorem necon3bii 2378

Description: Inference from equality to inequality. (Contributed by NM, 23-Feb-2005.)

Hypothesis

Ref	Expression
necon3bii.1	|- ( A = B <-> C = D )

Assertion

Ref	Expression
necon3bii	|- ( A =/= B <-> C =/= D )

Proof of Theorem necon3bii

Step	Hyp	Ref	Expression
1		necon3bii.1	. . 3 |- ( A = B <-> C = D )
2	1	necon3abii 2376	. 2 |- ( A =/= B <-> -. C = D )
3		df-ne 2341	. 2 |- ( C =/= D <-> -. C = D )
4	2, 3	bitr4i 186	1 |- ( A =/= B <-> C =/= D )

Syntax hints:   -. wn 3   <-> wb 104   = wceq 1348   =/= wne 2340

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 609  ax-in2 610

This theorem depends on definitions:  df-bi 116  df-ne 2341

This theorem is referenced by:  necom  2424  negne0bi  8192