reserve x1,x2,z for set;
reserve A,B for non empty set;
reserve f,g,h for Element of Funcs(A,COMPLEX);
reserve a,b for Complex;

theorem Th5:
  (ComplexFuncAdd(A)).(f,g) = (ComplexFuncAdd(A)).(g,f)
proof
  now
    let x be Element of A;
    thus ((ComplexFuncAdd(A)).(f,g)).x = g.x + f.x by Th1
      .= ((ComplexFuncAdd(A)).(g,f)).x by Th1;
  end;
  hence thesis by FUNCT_2:63;
end;
