Description: Two different ways of defining the collection from Exercise 3 of Munkres p. 83. (Contributed by ML, 18-Jul-2020)
Ref | Expression | ||
---|---|---|---|
Assertion | topdifinfeq | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | velpw | |
|
2 | sseqin2 | |
|
3 | 1 2 | bitri | |
4 | eqeq1 | |
|
5 | 3 4 | sylbi | |
6 | disj3 | |
|
7 | eqcom | |
|
8 | 6 7 | bitri | |
9 | 5 8 | bitr3di | |
10 | eqss | |
|
11 | ssdif0 | |
|
12 | 11 | bicomi | |
13 | 1 12 | anbi12i | |
14 | 10 13 | bitr4i | |
15 | 14 | baib | |
16 | 9 15 | orbi12d | |
17 | orcom | |
|
18 | 16 17 | bitrdi | |
19 | 18 | orbi2d | |
20 | 19 | bicomd | |
21 | 20 | rabbiia | |