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 Th58:
  for f being FinSequence st i in dom f holds (Rev f).i = f.(len f - i + 1)
proof
  let f be FinSequence;
  dom f = dom(Rev f) by Th57;
  hence thesis by Def3;
end;
