reserve a,x,y for object, A,B for set,
  l,m,n for Nat;
reserve X,Y for set, x for object,
  p,q for Function-yielding FinSequence,
  f,g,h for Function;
reserve m,n,k for Nat, R for Relation;
reserve i,j for Nat;

theorem Th96:
  for w being FinSequence,r being object,i being natural Number
  holds len (w+*(i,r))=len w
proof
  let w be FinSequence,r be object,i be natural Number;
  dom ( w+*(i,r))=dom w by Th29;
  then Seg len ( w+*(i,r))=dom w by FINSEQ_1:def 3
    .=Seg len w by FINSEQ_1:def 3;
  hence thesis by FINSEQ_1:6;
end;
