Description: Value of a singleton word if the symbol is a proper class. (Contributed by AV, 26-Mar-2022)
Ref | Expression | ||
---|---|---|---|
Assertion | s1prc | |- ( -. A e. _V -> <" A "> = <" (/) "> ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ids1 | |- <" A "> = <" ( _I ` A ) "> |
|
2 | fvprc | |- ( -. A e. _V -> ( _I ` A ) = (/) ) |
|
3 | 2 | s1eqd | |- ( -. A e. _V -> <" ( _I ` A ) "> = <" (/) "> ) |
4 | 1 3 | eqtrid | |- ( -. A e. _V -> <" A "> = <" (/) "> ) |