
theorem Th57:
  for L being non empty doubleLoopStr, A, B being non empty Subset
  of L st A c= B holds A-Ideal c= B-Ideal
proof
  let L be non empty doubleLoopStr, A,B be non empty Subset of L;
  assume
A1: A c= B;
  B c= B-Ideal by Def14;
  then A c= B-Ideal by A1;
  hence thesis by Def14;
end;
