Example 8.14. Find
the Cauchy principal value of
.
![[Graphics:Images/IntegralsRationalMod_gr_30.gif]](../Images/IntegralsRationalMod_gr_30.gif)
Explore Solution 8.14.
Method (i). Enter
the function
and
investigate the Cauchy Principal Value .
![[Graphics:../Images/IntegralsRationalMod_gr_34.gif]](../Images/IntegralsRationalMod_gr_34.gif)
![[Graphics:../Images/IntegralsRationalMod_gr_35.gif]](../Images/IntegralsRationalMod_gr_35.gif)
Method (ii). Enter
the function
and
locate the singularities.
![[Graphics:../Images/IntegralsRationalMod_gr_38.gif]](../Images/IntegralsRationalMod_gr_38.gif)
Determine which poles lie in the upper half plane ?
![[Graphics:../Images/IntegralsRationalMod_gr_40.gif]](../Images/IntegralsRationalMod_gr_40.gif)
![]()
Compute the residues at
,
and use the residue calculus to compute the value of the
integral.
![]()
![[Graphics:../Images/IntegralsRationalMod_gr_45.gif]](../Images/IntegralsRationalMod_gr_45.gif)
![[Graphics:../Images/IntegralsRationalMod_gr_46.gif]](../Images/IntegralsRationalMod_gr_46.gif)
Or, we can use Mathematica's integral table and evaluate the integral.
![]()
However, for this simple integral Mathematica's can find the correct answer without resorting to the PrincipalValue option.
![[Graphics:../Images/IntegralsRationalMod_gr_50.gif]](../Images/IntegralsRationalMod_gr_50.gif)
The above answer is correct too.