
theorem
  for D being set, p,q,r be Element of D* holds
  FlattenSeq <* p,q,r *> = p ^ q ^ r
proof
  let D be set, p,q,r be Element of D*;
  consider g being BinOp of D* such that
A1: for d1,d2 being Element of D* holds g.(d1,d2) = d1^d2 and
A2: FlattenSeq <* p,q,r *> = g "**" <* p,q,r *> by Def1;
  thus FlattenSeq <* p,q,r *> = g.(g.(p,q),r) by A2,FINSOP_1:14
    .= g.(p,q) ^ r by A1
    .= p ^ q ^ r by A1;
end;
