Description: Contraposition. Theorem *2.03 of WhiteheadRussell p. 100. (Contributed by NM, 29-Dec-1992) (Proof shortened by Wolf Lammen, 12-Feb-2013)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | con2 | |- ( ( ph -> -. ps ) -> ( ps -> -. ph ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | id | |- ( ( ph -> -. ps ) -> ( ph -> -. ps ) ) |
|
| 2 | 1 | con2d | |- ( ( ph -> -. ps ) -> ( ps -> -. ph ) ) |