Description: Double deduction introducing an antecedent. Deduction associated with a1d . Double deduction associated with ax-1 and a1i . (Contributed by NM, 17-Dec-2004) (Proof shortened by Mel L. O'Cat, 15-Jan-2008)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | a1dd.1 | |- ( ph -> ( ps -> ch ) ) |
|
| Assertion | a1dd | |- ( ph -> ( ps -> ( th -> ch ) ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | a1dd.1 | |- ( ph -> ( ps -> ch ) ) |
|
| 2 | ax-1 | |- ( ch -> ( th -> ch ) ) |
|
| 3 | 1 2 | syl6 | |- ( ph -> ( ps -> ( th -> ch ) ) ) |