theorem Th37:
  {a} |^ {b} = {a |^ b}
proof
A1: {b}" * {a} * {b} = {b"} * {a} * {b} by GROUP_2:3
    .= {b" * a} * {b} by GROUP_2:18
    .= {a |^ b} by GROUP_2:18;
  {a} |^ {b} c= {b}" * {a} * {b} & {a} |^ {b} <> {} by Th32,Th33;
  hence thesis by A1,ZFMISC_1:33;
end;
