Description: Virtual deduction identity rule for three virtual hypotheses. (Contributed by Alan Sare, 11-Jun-2011) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | idn3 | |- (. ph ,. ps ,. ch ->. ch ). |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | idd | |- ( ps -> ( ch -> ch ) ) |
|
| 2 | 1 | a1i | |- ( ph -> ( ps -> ( ch -> ch ) ) ) |
| 3 | 2 | dfvd3ir | |- (. ph ,. ps ,. ch ->. ch ). |