reserve X,Y,Z,X1,X2,Y1,Y2 for set, x,y,z,t,x1,x2 for object,
  f,g,h,f1,f2,g1,g2 for Function;

theorem
  dom curry' f = proj2 dom f
proof
  dom curry ~f = proj1 dom ~f by Def1;
  hence thesis by Th11;
end;
