Fig. A.8-1. Differential
volume element r dr dO dz
in cylindrical coordinates,
Cylindrical surface and differential line ele
of radius r ments dr, r dS, and dz. The
differential surface ele
ments are: (r dd)(dz) per
pendicular to the r direction
(intermediate shading);
(dz)(dr) perpendicular to the
direction (darkest shad
ing); and (dr)(r d6) perpen
dicular to the z direction
(lightest shading