Description: There does not exist exactly one set such that T. is true. (Contributed by Anthony Hart, 13-Sep-2011)
Ref | Expression | ||
---|---|---|---|
Assertion | neutru | |- -. E! x T. |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nexntru | |- -. E. x -. T. |
|
2 | eunex | |- ( E! x T. -> E. x -. T. ) |
|
3 | 1 2 | mto | |- -. E! x T. |