theorem
  UsedI*Loc (p +* r) c= UsedI*Loc p \/ UsedI*Loc r
proof
   rng(p +* r) c= rng p \/ rng r by FUNCT_4:17;
   then UsedI*Loc(p +* r) c= UsedI*Loc(rng p \/ rng r) by Lm5;
  hence UsedI*Loc(p +* r) c= UsedI*Loc p \/ UsedI*Loc r by Lm6;
end;
