theorem alleq1d (_G: wff) (_A1 _A2: set) (l: nat): $ _G -> _A1 == _A2 $ > $ _G -> (all _A1 l <-> all _A2 l) $;
_G -> _A1 == _A2
_G -> l = l
_G -> (all _A1 l <-> all _A2 l)