theorem Th9:
  c1 + <%c2%> = <%c1 + c2%>
  proof
A1:   dom <%c1 + c2%> = 1 = dom <%c2%> = dom (c1 + <%c2%>)
      by VALUED_1:def 2,AFINSQ_1:def 4;
    <%c1 + c2%>.0 = c1+(<%c2%>.0)
      .= (c1 + <%c2%>).0 by A1,AFINSQ_1:66,VALUED_1:def 2;
    hence thesis by A1,AFINSQ_1:def 4;
  end;
