Description: Introduce a left conjunct to both sides of a logical equivalence. (Contributed by NM, 3-Jan-1993) (Proof shortened by Wolf Lammen, 16-Nov-2013)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | anbi.1 | |- ( ph <-> ps ) |
|
| Assertion | anbi2i | |- ( ( ch /\ ph ) <-> ( ch /\ ps ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | anbi.1 | |- ( ph <-> ps ) |
|
| 2 | 1 | a1i | |- ( ch -> ( ph <-> ps ) ) |
| 3 | 2 | pm5.32i | |- ( ( ch /\ ph ) <-> ( ch /\ ps ) ) |