theorem Th10:
  ic in rng p & (ic = a :=len fa or ic = fa :=<0,...,0>a)
  implies a in UsedILoc p
proof
  assume that
A1: ic in rng p and
A2: ic = a :=len fa or ic = fa :=<0,...,0>a;
A3: UsedIntLoc ic = {a} by A2,SF_MASTR:18;
  UsedIntLoc ic c= UsedILoc p by A1,SF_MASTR:19;
  hence thesis by A3,ZFMISC_1:31;
end;
