Example 8.22. Show
that
.
![[Graphics:Images/IntegralsIndentedContourMod_gr_107.gif]](../Images/IntegralsIndentedContourMod_gr_107.gif)
Explore Solution 8.22.
Enter the function and
and
locate the singularities.
![[Graphics:../Images/IntegralsIndentedContourMod_gr_116.gif]](../Images/IntegralsIndentedContourMod_gr_116.gif)
Which poles lie in the upper half plane ? Which poles lie on the real axis ?
![[Graphics:../Images/IntegralsIndentedContourMod_gr_118.gif]](../Images/IntegralsIndentedContourMod_gr_118.gif)
![[Graphics:../Images/IntegralsIndentedContourMod_gr_119.gif]](../Images/IntegralsIndentedContourMod_gr_119.gif)
Compute the residues at
, and
use the residue calculus to compute the value of the integral.
![[Graphics:../Images/IntegralsIndentedContourMod_gr_122.gif]](../Images/IntegralsIndentedContourMod_gr_122.gif)
![[Graphics:../Images/IntegralsIndentedContourMod_gr_123.gif]](../Images/IntegralsIndentedContourMod_gr_123.gif)
![[Graphics:../Images/IntegralsIndentedContourMod_gr_124.gif]](../Images/IntegralsIndentedContourMod_gr_124.gif)
Warning. The indefinite integral of F[x] is g[x], but it cannot be used in any meaningful way to solve the problem at hand.
![[Graphics:../Images/IntegralsIndentedContourMod_gr_126.gif]](../Images/IntegralsIndentedContourMod_gr_126.gif)
Aside. We can use Mathematica's built in "PrincipalValue" option to evaluate the definite integral .
![[Graphics:../Images/IntegralsIndentedContourMod_gr_128.gif]](../Images/IntegralsIndentedContourMod_gr_128.gif)
Which is also the correct answer.