Description: The virtual deduction form of a 2-antecedent nested implication implies the 2-antecedent nested implication. (Contributed by Alan Sare, 21-Apr-2011) (Proof modification is discouraged.) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | dfvd2imp | |- ( (. ph ,. ps ->. ch ). -> ( ph -> ( ps -> ch ) ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dfvd2 | |- ( (. ph ,. ps ->. ch ). <-> ( ph -> ( ps -> ch ) ) ) |
|
2 | 1 | biimpi | |- ( (. ph ,. ps ->. ch ). -> ( ph -> ( ps -> ch ) ) ) |