The temperature T in a metal ball is inversely
proportional to the distance from the center of the ball, which we
take to be the origin. The temperature at the point (1, 2, 2) is
160°.
(a) Find the rate of change of T at (1, 2, 2) in the
direction toward the point (3, 1, 4).
(b) Show that at any point in the ball the direction of greatest
increase in temperature is given by a vector that points...