reserve Al for QC-alphabet;
reserve p,q,p1,p2,q1 for Element of CQC-WFF(Al),
  k for Element of NAT,
  f,f1,f2,g for FinSequence of CQC-WFF(Al),
  a,b,b1,b2,c,i,n for Nat;

theorem Th11:
  dom Sgm(seq(len g,len f)) = dom f
proof
  len Sgm(seq(len g,len f)) = len f by Th10;
  hence thesis by FINSEQ_3:29;
end;
