Description: Existence of a class of subsets. (Contributed by NM, 15-Jul-2006) (Proof shortened by Andrew Salmon, 25-Jul-2011)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | abssexg |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | pwexg | ||
| 2 | df-pw | ||
| 3 | 2 | eleq1i | |
| 4 | simpl | ||
| 5 | 4 | ss2abi | |
| 6 | ssexg | ||
| 7 | 5 6 | mpan | |
| 8 | 3 7 | sylbi | |
| 9 | 1 8 | syl |