Description: Define the class of positive integers. This is a "temporary" set used in the construction of complex numbers df-c , and is intended to be used only by the construction. (Contributed by NM, 15-Aug-1995) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | df-ni | |- N. = ( _om \ { (/) } ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 0 | cnpi | |- N. |
|
| 1 | com | |- _om |
|
| 2 | c0 | |- (/) |
|
| 3 | 2 | csn | |- { (/) } |
| 4 | 1 3 | cdif | |- ( _om \ { (/) } ) |
| 5 | 0 4 | wceq | |- N. = ( _om \ { (/) } ) |