Consider the spin-precession problem discussed in the text. It can also be solved in the Heisenberg picture. Using the Hamiltonian H = – (eB/mc) S_z = wS_z, write the Heisenberg equations of motion for the time-dependent operators S_x(t), S_y(t), and S_z(t). Solve them to obtain S_{x, y, z} as functions of time.