Description: Sethood of certain classes. (Contributed by BJ, 2-Apr-2019)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | bj-clexab | |- ( A e. V -> { x | { x } e. ( A " B ) } e. _V ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | imaexg | |- ( A e. V -> ( A " B ) e. _V ) |
|
| 2 | bj-snsetex | |- ( ( A " B ) e. _V -> { x | { x } e. ( A " B ) } e. _V ) |
|
| 3 | 1 2 | syl | |- ( A e. V -> { x | { x } e. ( A " B ) } e. _V ) |