Solution 2.

See text and/or instructor's solution manual.

Answer.   [Graphics:../Images/PoissonIntegralModHome_gr_48.gif].  

Alternative Answer.   [Graphics:../Images/PoissonIntegralModHome_gr_49.gif].  

Solution.   Use the Poisson's integral formula, Equation (11-12)   [Graphics:../Images/PoissonIntegralModHome_gr_50.gif],   and obtain  

            [Graphics:../Images/PoissonIntegralModHome_gr_51.gif]  

Using techniques from calculus we have the integration formulas

                    [Graphics:../Images/PoissonIntegralModHome_gr_52.gif],    and  
    
                    [Graphics:../Images/PoissonIntegralModHome_gr_53.gif],    and   
    
                    [Graphics:../Images/PoissonIntegralModHome_gr_54.gif].   

We obtain the solution as follows

            [Graphics:../Images/PoissonIntegralModHome_gr_55.gif]  

The function [Graphics:../Images/PoissonIntegralModHome_gr_56.gif] is continuous in the upper half-plane, and on the boundary [Graphics:../Images/PoissonIntegralModHome_gr_57.gif], except at the discontinuities [Graphics:../Images/PoissonIntegralModHome_gr_58.gif] and  [Graphics:../Images/PoissonIntegralModHome_gr_59.gif]  on the real axis.  

 

We are done.   

 

Aside.  We can let Mathematica double check our work.

[Graphics:../Images/PoissonIntegralModHome_gr_60.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_61.gif]


[Graphics:../Images/PoissonIntegralModHome_gr_62.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_63.gif]


[Graphics:../Images/PoissonIntegralModHome_gr_64.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_65.gif]


[Graphics:../Images/PoissonIntegralModHome_gr_66.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_67.gif]


[Graphics:../Images/PoissonIntegralModHome_gr_68.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_69.gif]

Using the identities    [Graphics:../Images/PoissonIntegralModHome_gr_70.gif],     [Graphics:../Images/PoissonIntegralModHome_gr_71.gif],     [Graphics:../Images/PoissonIntegralModHome_gr_72.gif]  

and    Log[Graphics:../Images/PoissonIntegralModHome_gr_73.gif],    will convert Mathematica's solution into the desired form:  

                    [Graphics:../Images/PoissonIntegralModHome_gr_74.gif].  

 

We are really done.   

 

Aside.  For illustration purposes we can graph the function   

                    [Graphics:../Images/PoissonIntegralModHome_gr_75.gif].   

                     [Graphics:../Images/PoissonIntegralModHome_gr_76.gif]

                     A contour graph of   [Graphics:../Images/PoissonIntegralModHome_gr_77.gif]

                     [Graphics:../Images/PoissonIntegralModHome_gr_78.gif]   for   [Graphics:../Images/PoissonIntegralModHome_gr_79.gif].  

                     [Graphics:../Images/PoissonIntegralModHome_gr_80.gif]

                     A contour graph of   [Graphics:../Images/PoissonIntegralModHome_gr_81.gif]

                     [Graphics:../Images/PoissonIntegralModHome_gr_82.gif]   for   [Graphics:../Images/PoissonIntegralModHome_gr_83.gif].  

 

                     [Graphics:../Images/PoissonIntegralModHome_gr_84.gif]

                    A contour graph of   [Graphics:../Images/PoissonIntegralModHome_gr_85.gif]

                    [Graphics:../Images/PoissonIntegralModHome_gr_86.gif]

 

We are really really done.   

 

Aside.  We can let Mathematica check out some boundary values.

[Graphics:../Images/PoissonIntegralModHome_gr_87.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_89.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_90.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_91.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_92.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_93.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_94.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_95.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_96.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_97.gif]

[Graphics:../Images/PoissonIntegralModHome_gr_98.gif]

We are really really really done.   

 

The Alternative Solution.

 

        From Example 11.12, the function  

                    [Graphics:../Images/PoissonIntegralModHome_gr_99.gif]  

is harmonic in the upper half-plane  [Graphics:../Images/PoissonIntegralModHome_gr_100.gif],  which takes on the boundary values  

                    [Graphics:../Images/PoissonIntegralModHome_gr_101.gif]  

                     [Graphics:../Images/PoissonIntegralModHome_gr_102.gif]

                    A graph of the terms   [Graphics:../Images/PoissonIntegralModHome_gr_103.gif].  

Using techniques from Section 11.2, we find that the function  

                    [Graphics:../Images/PoissonIntegralModHome_gr_104.gif]  

is harmonic in the upper half-plane and has the boundary values  [Graphics:../Images/PoissonIntegralModHome_gr_105.gif],    [Graphics:../Images/PoissonIntegralModHome_gr_106.gif],   and   [Graphics:../Images/PoissonIntegralModHome_gr_107.gif]  

                     [Graphics:../Images/PoissonIntegralModHome_gr_108.gif]

                    A graph of the terms   [Graphics:../Images/PoissonIntegralModHome_gr_109.gif].  

This function can be added to the function  [Graphics:../Images/PoissonIntegralModHome_gr_110.gif] in Example 11.12 to get

                    [Graphics:../Images/PoissonIntegralModHome_gr_111.gif]   

                    [Graphics:../Images/PoissonIntegralModHome_gr_112.gif]

                     [Graphics:../Images/PoissonIntegralModHome_gr_113.gif]

                    A graph of the intermediate function   [Graphics:../Images/PoissonIntegralModHome_gr_114.gif].  

Adjust the variables in  [Graphics:../Images/PoissonIntegralModHome_gr_115.gif] and rescale the output to obtain the desired solution  

                    [Graphics:../Images/PoissonIntegralModHome_gr_116.gif]   

                    [Graphics:../Images/PoissonIntegralModHome_gr_117.gif]

Graph Of The Alternative Solution.   For illustration purposes we can graph the alternative solution     

                    [Graphics:../Images/PoissonIntegralModHome_gr_118.gif].   

                     [Graphics:../Images/PoissonIntegralModHome_gr_119.gif]

                     A contour graph of the alternative solution   [Graphics:../Images/PoissonIntegralModHome_gr_120.gif]   

                     [Graphics:../Images/PoissonIntegralModHome_gr_121.gif]   for   [Graphics:../Images/PoissonIntegralModHome_gr_122.gif].  

                     [Graphics:../Images/PoissonIntegralModHome_gr_123.gif]

                     A contour graph of the alternative solution   [Graphics:../Images/PoissonIntegralModHome_gr_124.gif]   

                     [Graphics:../Images/PoissonIntegralModHome_gr_125.gif]   for   [Graphics:../Images/PoissonIntegralModHome_gr_126.gif].  

 

                     [Graphics:../Images/PoissonIntegralModHome_gr_127.gif]

                    A graph of the alternative solution   [Graphics:../Images/PoissonIntegralModHome_gr_128.gif]

                    [Graphics:../Images/PoissonIntegralModHome_gr_129.gif]

 
















 

This solution is complements of the authors.

 

































 

(c) 2008 John H. Mathews, Russell W. Howell