Description: A subset is closed iff it contains its own closure. (Contributed by NM, 31-Jan-2008)
Ref | Expression | ||
---|---|---|---|
Hypothesis | clscld.1 | |
|
Assertion | iscld4 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | clscld.1 | |
|
2 | 1 | iscld3 | |
3 | eqss | |
|
4 | 1 | sscls | |
5 | 4 | biantrud | |
6 | 3 5 | bitr4id | |
7 | 2 6 | bitrd | |