let C, D be non empty set ; :: thesis: for f being Function of C,D
for F being BinOp of D st F is having_a_unity holds
( F .: ((C --> ()),f) = f & F .: (f,(C --> ())) = f )

let f be Function of C,D; :: thesis: for F being BinOp of D st F is having_a_unity holds
( F .: ((C --> ()),f) = f & F .: (f,(C --> ())) = f )

let F be BinOp of D; :: thesis: ( F is having_a_unity implies ( F .: ((C --> ()),f) = f & F .: (f,(C --> ())) = f ) )
set e = the_unity_wrt F;
reconsider g = C --> () as Function of C,D ;
assume A1: F is having_a_unity ; :: thesis: ( F .: ((C --> ()),f) = f & F .: (f,(C --> ())) = f )
now :: thesis: for c being Element of C holds (F .: (g,f)) . c = f . c
let c be Element of C; :: thesis: (F .: (g,f)) . c = f . c
thus (F .: (g,f)) . c = F . ((g . c),(f . c)) by FUNCOP_1:37
.= F . ((),(f . c))
.= f . c by ; :: thesis: verum
end;
hence F .: ((C --> ()),f) = f by FUNCT_2:63; :: thesis: F .: (f,(C --> ())) = f
now :: thesis: for c being Element of C holds (F .: (f,g)) . c = f . c
let c be Element of C; :: thesis: (F .: (f,g)) . c = f . c
thus (F .: (f,g)) . c = F . ((f . c),(g . c)) by FUNCOP_1:37
.= F . ((f . c),())
.= f . c by ; :: thesis: verum
end;
hence F .: (f,(C --> ())) = f by FUNCT_2:63; :: thesis: verum