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Description: The empty set is a continuous function. (Contributed by Glauco Siliprandi, 11-Dec-2019)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | 0cnf | |- (/) e. ( { (/) } Cn { (/) } ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | f0 | |- (/) : (/) --> (/) |
|
| 2 | cnv0 | |- `' (/) = (/) |
|
| 3 | 2 | imaeq1i | |- ( `' (/) " x ) = ( (/) " x ) |
| 4 | 0ima | |- ( (/) " x ) = (/) |
|
| 5 | 3 4 | eqtri | |- ( `' (/) " x ) = (/) |
| 6 | 0ex | |- (/) e. _V |
|
| 7 | 6 | snid | |- (/) e. { (/) } |
| 8 | 5 7 | eqeltri | |- ( `' (/) " x ) e. { (/) } |
| 9 | 8 | rgenw | |- A. x e. { (/) } ( `' (/) " x ) e. { (/) } |
| 10 | sn0topon | |- { (/) } e. ( TopOn ` (/) ) |
|
| 11 | iscn | |- ( ( { (/) } e. ( TopOn ` (/) ) /\ { (/) } e. ( TopOn ` (/) ) ) -> ( (/) e. ( { (/) } Cn { (/) } ) <-> ( (/) : (/) --> (/) /\ A. x e. { (/) } ( `' (/) " x ) e. { (/) } ) ) ) |
|
| 12 | 10 10 11 | mp2an | |- ( (/) e. ( { (/) } Cn { (/) } ) <-> ( (/) : (/) --> (/) /\ A. x e. { (/) } ( `' (/) " x ) e. { (/) } ) ) |
| 13 | 1 9 12 | mpbir2an | |- (/) e. ( { (/) } Cn { (/) } ) |