reserve A,B,X,X1,Y,Y1,Y2,Z for set, a,x,y,z for object;
reserve P,R for Relation of X,Y;

theorem
  R.:(R"Y) = rng R & R"(R.:X) = dom R
proof
  R"Y = dom R & R.:X = rng R by Th22;
  hence thesis by RELAT_1:113,134;
end;
