
theorem LM0710:
  for x be Element of BOOLEAN*
  st x in rng Nat2BL
  holds 1<= len x
  proof
    let x be Element of BOOLEAN*;
    assume x in rng Nat2BL;
    then
    consider L be Element of NAT such that
    H5: x = Nat2BL.L by FUNCT_2:113;
    x = (LenBSeq L) -BinarySequence L by Def2,H5;
    then 0 <> len x;
    then 0 < len x;
    then 1 + 0 <= len x by NAT_1:13;
    hence thesis;
  end;
