Example 8.14.  Find the Cauchy principal value of  [Graphics:Images/IntegralsRationalMod_gr_29.gif].

[Graphics:Images/IntegralsRationalMod_gr_30.gif]

Explore Solution 8.14.

Method (i).  Enter the function  [Graphics:../Images/IntegralsRationalMod_gr_32.gif]  and investigate the  Cauchy Principal Value .

[Graphics:../Images/IntegralsRationalMod_gr_33.gif]





[Graphics:../Images/IntegralsRationalMod_gr_34.gif]

[Graphics:../Images/IntegralsRationalMod_gr_35.gif]

 

 

 

 

Method (ii).  Enter the function  [Graphics:../Images/IntegralsRationalMod_gr_36.gif]  and locate the singularities.

[Graphics:../Images/IntegralsRationalMod_gr_37.gif]




[Graphics:../Images/IntegralsRationalMod_gr_38.gif]

 

 

 

Determine which poles lie in the upper half plane ?

[Graphics:../Images/IntegralsRationalMod_gr_39.gif]


[Graphics:../Images/IntegralsRationalMod_gr_40.gif]

[Graphics:../Images/IntegralsRationalMod_gr_41.gif]

 

 

Compute the residues at  [Graphics:../Images/IntegralsRationalMod_gr_42.gif], and use the residue calculus to compute the value of the integral.

[Graphics:../Images/IntegralsRationalMod_gr_43.gif]





[Graphics:../Images/IntegralsRationalMod_gr_44.gif]

[Graphics:../Images/IntegralsRationalMod_gr_45.gif]

[Graphics:../Images/IntegralsRationalMod_gr_46.gif]

 

 

 

Or, we can use Mathematica's integral table and evaluate the integral.

[Graphics:../Images/IntegralsRationalMod_gr_47.gif]

[Graphics:../Images/IntegralsRationalMod_gr_48.gif]

 

 

However, for this simple integral Mathematica's can find the correct answer without resorting to the PrincipalValue option.

[Graphics:../Images/IntegralsRationalMod_gr_49.gif]





[Graphics:../Images/IntegralsRationalMod_gr_50.gif]

The above answer is correct too.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) 2006 John H. Mathews, Russell W. Howell