Description: If A is contained in B , then ( C \ B ) is contained in ( C \ A ) . Deduction form of sscon . (Contributed by David Moews, 1-May-2017)
Ref | Expression | ||
---|---|---|---|
Hypothesis | ssdifd.1 | |
|
Assertion | sscond | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssdifd.1 | |
|
2 | sscon | |
|
3 | 1 2 | syl | |