Example 8.22.  Show that  [Graphics:Images/IntegralsIndentedContourMod_gr_106.gif].    

[Graphics:Images/IntegralsIndentedContourMod_gr_107.gif]

Explore Solution 8.22.

Enter the function and  [Graphics:../Images/IntegralsIndentedContourMod_gr_114.gif]  and locate the singularities.

[Graphics:../Images/IntegralsIndentedContourMod_gr_115.gif]




[Graphics:../Images/IntegralsIndentedContourMod_gr_116.gif]

 

 

 

Which poles lie in the upper half plane ?  Which poles lie on the real axis ?

[Graphics:../Images/IntegralsIndentedContourMod_gr_117.gif]




[Graphics:../Images/IntegralsIndentedContourMod_gr_118.gif]

[Graphics:../Images/IntegralsIndentedContourMod_gr_119.gif]

 

 

 

Compute the residues at  [Graphics:../Images/IntegralsIndentedContourMod_gr_120.gif],  and use the residue calculus to compute the value of the integral.

[Graphics:../Images/IntegralsIndentedContourMod_gr_121.gif]





[Graphics:../Images/IntegralsIndentedContourMod_gr_122.gif]

[Graphics:../Images/IntegralsIndentedContourMod_gr_123.gif]

[Graphics:../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_125.gif]



[Graphics:../Images/IntegralsIndentedContourMod_gr_126.gif]

 

 

 

Aside. We can use Mathematica's built in "PrincipalValue" option to evaluate the definite integral .

[Graphics:../Images/IntegralsIndentedContourMod_gr_127.gif]




[Graphics:../Images/IntegralsIndentedContourMod_gr_128.gif]

Which is also the correct answer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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