reserve i,j,k,n,m for Nat,
  x,y,z,y1,y2 for object, X,Y,D for set,
  p,q for XFinSequence;
reserve k1,k2 for Nat;

theorem :: FINSEQ_8:6
  len p<=k implies mid(p,1,k)=p
proof
  assume
A1: len p<=k;
  thus mid(p,1,k)=p|k by Th16
    .=p by A1,AFINSQ_1:52;
end;
