Hi [start code] f(x)=O(g(x))\mbox{ as }x\to a if and only if there exist positive numbers d and M such that |f(x)| \le \; M |g(x)|\mbox{ for }|x - a| < \delta. If g(x) is non-zero for values of x [end code] Is the | enclosing the functions used to denote order of growth? Cheers Paul