theorem funceq3d (_G: wff) (F A _B1 _B2: set): $ _G -> _B1 == _B2 $ > $ _G -> (func F A _B1 <-> func F A _B2) $;
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | eqsidd | _G -> F == F | |
| 2 | eqsidd | _G -> A == A | |
| 3 | hyp _h | _G -> _B1 == _B2 | |
| 4 | 1, 2, 3 | funceqd | _G -> (func F A _B1 <-> func F A _B2) |