and neglecting all the terms in the expansion except the first two. The first
term neglected is proportional to x2, and thus the error involved in each step
of this approximation is also proportional to x2. However, the commutative
error involved after M steps in the direction of length L is proportional to x
since Mx2 (L/x)x2 Lx. Therefore, the smaller the x, the smaller
the error, and thus the more accurate the approximation.