Description: Introduce a right conjunct to both sides of a logical equivalence. (Contributed by NM, 12-Mar-1993) (Proof shortened by Wolf Lammen, 16-Nov-2013)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | anbi.1 | |- ( ph <-> ps ) |
|
| Assertion | anbi1i | |- ( ( ph /\ ch ) <-> ( ps /\ ch ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | anbi.1 | |- ( ph <-> ps ) |
|
| 2 | 1 | a1i | |- ( ch -> ( ph <-> ps ) ) |
| 3 | 2 | pm5.32ri | |- ( ( ph /\ ch ) <-> ( ps /\ ch ) ) |