Theorem nelcon3d 2446

Description: Contrapositive law deduction for negated membership. (Contributed by AV, 28-Jan-2020.)

Hypothesis

Ref	Expression
nelcon3d.1	|- ( ph -> ( A e. B -> C e. D ) )

Assertion

Ref	Expression
nelcon3d	|- ( ph -> ( C e/ D -> A e/ B ) )

Proof of Theorem nelcon3d

Step	Hyp	Ref	Expression
1		nelcon3d.1	. . 3 |- ( ph -> ( A e. B -> C e. D ) )
2	1	con3d 626	. 2 |- ( ph -> ( -. C e. D -> -. A e. B ) )
3		df-nel 2436	. 2 |- ( C e/ D <-> -. C e. D )
4		df-nel 2436	. 2 |- ( A e/ B <-> -. A e. B )
5	2, 3, 4	3imtr4g 204	1 |- ( ph -> ( C e/ D -> A e/ B ) )

Syntax hints:   -. wn 3   -> wi 4   e. wcel 2141   e/ wnel 2435

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-nel 2436

This theorem is referenced by:  isnmgm  12614