Description: Absorption of redundant internal disjunct. Compare Theorem *4.45 of WhiteheadRussell p. 119. (Contributed by NM, 21-Jun-1993) (Proof shortened by Wolf Lammen, 28-Feb-2014)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | orabs | |- ( ph <-> ( ( ph \/ ps ) /\ ph ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | orc | |- ( ph -> ( ph \/ ps ) ) |
|
| 2 | 1 | pm4.71ri | |- ( ph <-> ( ( ph \/ ps ) /\ ph ) ) |