Theorem necon2bi 2395

Description: Contrapositive inference for inequality. (Contributed by NM, 1-Apr-2007.)

Hypothesis

Ref	Expression
necon2bi.1	|- ( ph -> A =/= B )

Assertion

Ref	Expression
necon2bi	|- ( A = B -> -. ph )

Proof of Theorem necon2bi

Step	Hyp	Ref	Expression
1		necon2bi.1	. . 3 |- ( ph -> A =/= B )
2	1	neneqd 2361	. 2 |- ( ph -> -. A = B )
3	2	con2i 622	1 |- ( A = B -> -. ph )

Syntax hints:   -. wn 3   -> wi 4   = wceq 1348   =/= wne 2340

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-in1 609  ax-in2 610

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

This theorem is referenced by:  minel  3476  rzal  3512  difsnb  3723  fin0  6863  0npi  7275  0nsr  7711  renfdisj  7979  nltpnft  9771  ngtmnft  9774  xrrebnd  9776  hashnncl  10730  rennim  10966  pceq0  12275