Derive Eq. 6.3. [Here's one way to do it: Assume the dipole is an infinitesimal square, of side 6 (if it's not, chop it up into squares, and apply the argument to each one). Choose axes as shown in Fig. 6.8, and calculate F = I f(dl x B) along each of the four sides. Expand B in a Taylor series??on the right side, for instance, For a more sophisticated method, see Prob.6.22.]

B = B(0.6.z) = B(0.0. 2) + 2 (0,0.2)