let f, g be Function; for x, y being object st [x,y] in dom f & g = (curry' f) . y holds
( x in dom g & g . x = f . (x,y) )
let x, y be object ; ( [x,y] in dom f & g = (curry' f) . y implies ( x in dom g & g . x = f . (x,y) ) )
assume
[x,y] in dom f
; ( not g = (curry' f) . y or ( x in dom g & g . x = f . (x,y) ) )
then A1:
[y,x] in dom (~ f)
by FUNCT_4:42;
assume A2:
g = (curry' f) . y
; ( x in dom g & g . x = f . (x,y) )
then
g . x = (~ f) . (y,x)
by A1, Th13;
hence
( x in dom g & g . x = f . (x,y) )
by A1, A2, Th13, FUNCT_4:43; verum