reserve p,q,r for FinSequence;
reserve u,v,x,y,y1,y2,z for object, A,D,X,Y for set;
reserve i,j,k,l,m,n for Nat;

theorem Th33:
  <* x *> <> <* y,z *>
proof
  len<* x *> = 1 by FINSEQ_1:40;
  hence thesis by FINSEQ_1:44;
end;
