Example 3.13. Show
that
is
a harmonic function and find the harmonic
conjugate
.
Explore Solution 3.13.
Enter the function u[x,y], do a step by step construction.
![[Graphics:../Images/HarmonicFunctionMod._gr_126.gif]](../Images/HarmonicFunctionMod._gr_126.gif)
![[Graphics:../Images/HarmonicFunctionMod._gr_127.gif]](../Images/HarmonicFunctionMod._gr_127.gif)
![[Graphics:../Images/HarmonicFunctionMod._gr_129.gif]](../Images/HarmonicFunctionMod._gr_129.gif)
![]()
![[Graphics:../Images/HarmonicFunctionMod._gr_132.gif]](../Images/HarmonicFunctionMod._gr_132.gif)
![[Graphics:../Images/HarmonicFunctionMod._gr_133.gif]](../Images/HarmonicFunctionMod._gr_133.gif)
![[Graphics:../Images/HarmonicFunctionMod._gr_135.gif]](../Images/HarmonicFunctionMod._gr_135.gif)
![[Graphics:../Images/HarmonicFunctionMod._gr_136.gif]](../Images/HarmonicFunctionMod._gr_136.gif)
We are done!
Aside. We can also
construct v[x,y] by the following alternative method.
Enter the function u[x,y], and determine if it is a harmonic function. If so, proceed with the construction of the harmonic conjugate v[x,y].
![[Graphics:../Images/HarmonicFunctionMod._gr_138.gif]](../Images/HarmonicFunctionMod._gr_138.gif)
Form the analytic function f[z] = u[x,y]+ i v[x,y] and verify that the Cauchy-Riemann equations hold.
![[Graphics:../Images/HarmonicFunctionMod._gr_140.gif]](../Images/HarmonicFunctionMod._gr_140.gif)
Therefore
is the harmonic conjugate of
.
Aside. We can use Mathematica to get the
standard form of an analytic function.
![[Graphics:../Images/HarmonicFunctionMod._gr_144.gif]](../Images/HarmonicFunctionMod._gr_144.gif)