Theorem necon4abid 2581

Description: Contrapositive law deduction for inequality. (Contributed by NM, 11-Jan-2008.)

Hypothesis

Ref	Expression
necon4abid.1	|- (ph -> (A =/= B <-> -. ps))

Assertion

Ref	Expression
necon4abid	|- (ph -> (A = B <-> ps))

Proof of Theorem necon4abid

Step	Hyp	Ref	Expression
1		df-ne 2519	. . 3 |- (A =/= B <-> -. A = B)
2		necon4abid.1	. . 3 |- (ph -> (A =/= B <-> -. ps))
3	1, 2	syl5bbr 250	. 2 |- (ph -> (-. A = B <-> -. ps))
4	3	con4bid 284	1 |- (ph -> (A = B <-> ps))

Syntax hints:  -. wn 3   -> wi 4   <-> wb 176   = wceq 1642   =/= wne 2517

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 177  df-ne 2519

This theorem is referenced by:  necon4bbid  2582