theorem Th24:
  for f being non constant standard special_circular_sequence
  holds LeftComp f is open & RightComp f is open
proof
  let f be non constant standard special_circular_sequence;
  LeftComp f is_a_component_of (L~f)` by GOBOARD9:def 1;
  hence LeftComp f is open by Th8;
  RightComp f is_a_component_of (L~f)` by GOBOARD9:def 2;
  hence thesis by Th8;
end;
