Cylindrical Co-ordinate System :
For cylindrical coordinate systems we have 
a point 
is determined as the point of intersection of a cylindrical surface r = r0, half plane containing the z-axis and making an angle 
; with the xz plane and a plane parallel to xy plane located at z=z0 as shown in figure 7 on next page.
In cylindrical coordinate system, the unit vectors satisfy the following relations
A vector 
can be written as , 
...........................(1.24)
The differential length is defined as,
......................(1.25)
.....................(1.23)