Theorem sscond 3259

Description: If A is contained in B, then ( C \ B ) is contained in ( C \ A ). Deduction form of sscon 3256. (Contributed by David Moews, 1-May-2017.)

Hypothesis

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

Assertion

Ref	Expression
sscond	|- ( ph -> ( C \ B ) C_ ( C \ A ) )

Proof of Theorem sscond

Step	Hyp	Ref	Expression
1		ssdifd.1	. 2 |- ( ph -> A C_ B )
2		sscon 3256	. 2 |- ( A C_ B -> ( C \ B ) C_ ( C \ A ) )
3	1, 2	syl 14	1 |- ( ph -> ( C \ B ) C_ ( C \ A ) )

Syntax hints:   -> wi 4   \ cdif 3113   C_ wss 3116

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 604  ax-in2 605  ax-io 699  ax-5 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-10 1493  ax-11 1494  ax-i12 1495  ax-bndl 1497  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523  ax-ext 2147

This theorem depends on definitions:  df-bi 116  df-tru 1346  df-nf 1449  df-sb 1751  df-clab 2152  df-cleq 2158  df-clel 2161  df-nfc 2297  df-v 2728  df-dif 3118  df-in 3122  df-ss 3129

This theorem is referenced by:  ssdif2d  3261  setsresg  12432