Description: A regular space is R_1, which means that any two topologically distinct points can be separated by neighborhoods. (Contributed by Mario Carneiro, 25-Aug-2015)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | regr1 | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | regtop | ||
| 2 | toptopon2 | ||
| 3 | 1 2 | sylib | |
| 4 | eqid | ||
| 5 | 4 | regr1lem2 | |
| 6 | 3 5 | mpancom |