Theorem sscond 3344

Description: If A is contained in B, then ( C \ B ) is contained in ( C \ A ). Deduction form of sscon 3341. (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 3341	. 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 3197   C_ wss 3200

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 619  ax-in2 620  ax-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-tru 1400  df-nf 1509  df-sb 1811  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2363  df-v 2804  df-dif 3202  df-in 3206  df-ss 3213

This theorem is referenced by:  ssdif2d  3346  setsresg  13121