Description: Theorem about subsets of the difference of unions. (Contributed by ML, 29-Mar-2021)
Ref | Expression | ||
---|---|---|---|
Assertion | inunissunidif | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | reldisj | |
|
2 | difunieq | |
|
3 | sstr | |
|
4 | 2 3 | mpan2 | |
5 | 1 4 | syl6bi | |
6 | 5 | com12 | |
7 | difss | |
|
8 | 7 | unissi | |
9 | sstr | |
|
10 | 8 9 | mpan2 | |
11 | 6 10 | impbid1 | |