reserve i,j,k,n for Nat;
reserve D for non empty set,
  p for Element of D,
  f,g for FinSequence of D;

theorem Th15:
  (<*p*>^f)/.1 = p
proof
  len(<*p*>^f) = 1 + len f by Th8;
  then 1 <= len(<*p*>^f) by NAT_1:11;
  then 1 in dom(<*p*>^f) by FINSEQ_3:25;
  then (<*p*>^f)/.1 = (<*p*>^f).1 by PARTFUN1:def 6;
  hence thesis by FINSEQ_1:41;
end;
