Figure 19.17.8: 
,

,

.
Cauchy principal values are shown when

.
The function is asymptotic to

as

, and to

as

.
As

it has the limit

.
When

, it reduces to

.
If

, then it has the value

when

, and

when

.
See (
19.20.10), (
19.20.11), and
(
19.20.8) for the cases

,

, and

, respectively.
3D
Help