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Theorem necon4d 2579
Description: Contrapositive inference for inequality. (Contributed by NM, 2-Apr-2007.) (Proof shortened by Andrew Salmon, 25-May-2011.)
Hypothesis
Ref Expression
necon4d.1
Assertion
Ref Expression
necon4d

Proof of Theorem necon4d
StepHypRef Expression
1 necon4d.1 . . 3
21necon2bd 2565 . 2
3 nne 2520 . 2
42, 3syl6ib 217 1
Colors of variables: wff setvar class
Syntax hints:   wn 3   wi 4   wceq 1642   wne 2516
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 2518
This theorem is referenced by:  tfin11  4493
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