Theorem ssneld 3185

Description: If a class is not in another class, it is also not in a subclass of that class. Deduction form. (Contributed by David Moews, 1-May-2017.)

Hypothesis

Ref	Expression
ssneld.1	|- ( ph -> A C_ B )

Assertion

Ref	Expression
ssneld	|- ( ph -> ( -. C e. B -> -. C e. A ) )

Proof of Theorem ssneld

Step	Hyp	Ref	Expression
1		ssneld.1	. . 3 |- ( ph -> A C_ B )
2	1	sseld 3182	. 2 |- ( ph -> ( C e. A -> C e. B ) )
3	2	con3d 632	1 |- ( ph -> ( -. C e. B -> -. C e. A ) )

Syntax hints:   -. wn 3   -> wi 4   e. wcel 2167   C_ wss 3157

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616  ax-5 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-11 1520  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549  ax-ext 2178

This theorem depends on definitions:  df-bi 117  df-nf 1475  df-sb 1777  df-clab 2183  df-cleq 2189  df-clel 2192  df-in 3163  df-ss 3170

This theorem is referenced by:  ssneldd  3186  sumdc  11523  summodclem2a  11546  zsumdc  11549  isumss2  11558  zproddc  11744  prodssdc  11754  decidin  15443