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Description: The preimage of a nonempty set is nonempty. (Contributed by Thierry Arnoux, 9-Jun-2024)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | preiman0 | |- ( ( Fun F /\ A C_ ran F /\ A =/= (/) ) -> ( `' F " A ) =/= (/) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-rn | |- ran F = dom `' F |
|
| 2 | 1 | ineq1i | |- ( ran F i^i ( A i^i ran F ) ) = ( dom `' F i^i ( A i^i ran F ) ) |
| 3 | dfss2 | |- ( A C_ ran F <-> ( A i^i ran F ) = A ) |
|
| 4 | 3 | biimpi | |- ( A C_ ran F -> ( A i^i ran F ) = A ) |
| 5 | 4 | ineq2d | |- ( A C_ ran F -> ( ran F i^i ( A i^i ran F ) ) = ( ran F i^i A ) ) |
| 6 | sseqin2 | |- ( A C_ ran F <-> ( ran F i^i A ) = A ) |
|
| 7 | 6 | biimpi | |- ( A C_ ran F -> ( ran F i^i A ) = A ) |
| 8 | 5 7 | eqtrd | |- ( A C_ ran F -> ( ran F i^i ( A i^i ran F ) ) = A ) |
| 9 | 8 | 3ad2ant2 | |- ( ( Fun F /\ A C_ ran F /\ ( `' F " A ) = (/) ) -> ( ran F i^i ( A i^i ran F ) ) = A ) |
| 10 | fimacnvinrn | |- ( Fun F -> ( `' F " A ) = ( `' F " ( A i^i ran F ) ) ) |
|
| 11 | 10 | eqeq1d | |- ( Fun F -> ( ( `' F " A ) = (/) <-> ( `' F " ( A i^i ran F ) ) = (/) ) ) |
| 12 | 11 | biimpa | |- ( ( Fun F /\ ( `' F " A ) = (/) ) -> ( `' F " ( A i^i ran F ) ) = (/) ) |
| 13 | 12 | 3adant2 | |- ( ( Fun F /\ A C_ ran F /\ ( `' F " A ) = (/) ) -> ( `' F " ( A i^i ran F ) ) = (/) ) |
| 14 | imadisj | |- ( ( `' F " ( A i^i ran F ) ) = (/) <-> ( dom `' F i^i ( A i^i ran F ) ) = (/) ) |
|
| 15 | 13 14 | sylib | |- ( ( Fun F /\ A C_ ran F /\ ( `' F " A ) = (/) ) -> ( dom `' F i^i ( A i^i ran F ) ) = (/) ) |
| 16 | 2 9 15 | 3eqtr3a | |- ( ( Fun F /\ A C_ ran F /\ ( `' F " A ) = (/) ) -> A = (/) ) |
| 17 | 16 | 3expia | |- ( ( Fun F /\ A C_ ran F ) -> ( ( `' F " A ) = (/) -> A = (/) ) ) |
| 18 | 17 | necon3d | |- ( ( Fun F /\ A C_ ran F ) -> ( A =/= (/) -> ( `' F " A ) =/= (/) ) ) |
| 19 | 18 | 3impia | |- ( ( Fun F /\ A C_ ran F /\ A =/= (/) ) -> ( `' F " A ) =/= (/) ) |