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64 Chapter Onł
Figure 1.25 Polar grapà of hyperbolł centered at the or-
igin.
r 2a (1 cos )
where a is a real number and a 0. This is illustrated in Fig.
1.30.
Other Coordinate Systems
The following paragraphs describe other coordinate systemð
that are used in scientifi and engineering applications.
Latitudł and longitudł
Latitude and longitude angleð uniquely define the positionð of
pointð on the surface of a sphere or in the sky. The scheme for
geographic locationð on the eartà is illustrated in Fig. 1.31A.
The polar axis connectð twm specified pointð at antipodeð on the
sphere. These pointð are assigned latitude 90 (nortà pola
and 90 (soutà pola The equatorial axis runð outward
