Description: An open subset equals its own interior. (Contributed by Mario Carneiro, 30-Dec-2016)
Ref | Expression | ||
---|---|---|---|
Assertion | isopn3i | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | simpr | |
|
2 | elssuni | |
|
3 | eqid | |
|
4 | 3 | isopn3 | |
5 | 2 4 | sylan2 | |
6 | 1 5 | mpbid | |