Description: The outer measure of a set is a nonnegative extended real. (Contributed by Glauco Siliprandi, 17-Aug-2020)
Ref | Expression | ||
---|---|---|---|
Hypotheses | omecl.o | |
|
omecl.x | |
||
omecl.ss | |
||
Assertion | omecl | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | omecl.o | |
|
2 | omecl.x | |
|
3 | omecl.ss | |
|
4 | 1 2 | omef | |
5 | 2 | a1i | |
6 | 1 | dmexd | |
7 | 6 | uniexd | |
8 | 5 7 | eqeltrd | |
9 | 8 3 | ssexd | |
10 | elpwg | |
|
11 | 9 10 | syl | |
12 | 3 11 | mpbird | |
13 | 4 12 | ffvelcdmd | |