Example 3.11.  If  [Graphics:Images/HarmonicFunctionMod._gr_45.gif],  then  [Graphics:Images/HarmonicFunctionMod._gr_46.gif];   hence u is a harmonic function for all z.  We find that [Graphics:Images/HarmonicFunctionMod._gr_47.gif] is also a harmonic function and that

            [Graphics:Images/HarmonicFunctionMod._gr_48.gif],   and   

            [Graphics:Images/HarmonicFunctionMod._gr_49.gif].

Therefore v is a harmonic conjugate of u, and the function f given by  

            [Graphics:Images/HarmonicFunctionMod._gr_50.gif]  

is an analytic function.

Explore Solution 3.11.

Enter the functions u[x,y] and v[x,y] and show that the Cauchy-Riemann equations hold.

[Graphics:../Images/HarmonicFunctionMod._gr_51.gif]




[Graphics:../Images/HarmonicFunctionMod._gr_52.gif]

 

 

The Cauchy-Riemann equations hold, therefore  [Graphics:../Images/HarmonicFunctionMod._gr_53.gif]  is analytic.  It follows that both  [Graphics:../Images/HarmonicFunctionMod._gr_54.gif]  and   [Graphics:../Images/HarmonicFunctionMod._gr_55.gif] are harmonic functions.

Aside.  The underlying complex function is  [Graphics:../Images/HarmonicFunctionMod._gr_56.gif].  

[Graphics:../Images/HarmonicFunctionMod._gr_57.gif]




[Graphics:../Images/HarmonicFunctionMod._gr_58.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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