Description: Lemma for issiga and isrnsiga . The class of sigma-algebras with base set o is a set. Note: a more generic version with ( O e. _V -> ... ) could be useful for sigaval . (Contributed by Thierry Arnoux, 24-Oct-2016)
Ref | Expression | ||
---|---|---|---|
Assertion | sigaex | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-rab | |
|
2 | velpw | |
|
3 | 2 | anbi1i | |
4 | 3 | abbii | |
5 | 1 4 | eqtri | |
6 | vex | |
|
7 | pwexg | |
|
8 | pwexg | |
|
9 | 6 7 8 | mp2b | |
10 | 9 | rabex | |
11 | 5 10 | eqeltrri | |