theorem Th1:
  for n be Nat, h be FinSequence of TOP-REAL n st len h
  >= 2 holds h/.len h in LSeg(h,len h-'1)
proof
  let n be Nat;
  let h be FinSequence of TOP-REAL n;
  set i = len h;
  assume
A1: len h >= 2;
  then
A2: 2-1 <= i-1 by XREAL_1:9;
  i-'1+1 = len h by A1,XREAL_1:235,XXREAL_0:2;
  hence thesis by A2,TOPREAL1:21;
end;
