Description: Deduction introducing a disjunct. A translation of natural deduction rule \/ IL ( \/ insertion left), see natded . (Contributed by NM, 11-Apr-2008) (Proof shortened by Wolf Lammen, 3-Oct-2013)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | orcd.1 | |- ( ph -> ps ) |
|
| Assertion | olcd | |- ( ph -> ( ch \/ ps ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | orcd.1 | |- ( ph -> ps ) |
|
| 2 | 1 | orcd | |- ( ph -> ( ps \/ ch ) ) |
| 3 | 2 | orcomd | |- ( ph -> ( ch \/ ps ) ) |