The reader is asked to show, that the drag polar of Figure 8.4 can be approximated by a parabolic

drag polar with A=15.6, e=0.82 and C= 0.0150. The speed for best glide performance, using

sea-level density data can then be computed from Egn (8,29) as 20.9 m/sec. This agrees closely with

the data of Table 8.1 which use the actual drag polar.