Examples from Section 14.1

The first is an animation of Figure 11, p. 883 (14.1):
Level Curves Figure 11
The next is an animation of Figure 17, p. 885. Again, we're showing level curves.
Level Curves Figure 17
This is an animation of Figure 19, plots (a) and (b).
Figure 19
This is an animation of Figure 19, plots (c) and (d).
Figure 19