Exercise 9.  Show that the following functions are entire (see Definition 3.2).  

9 (a).  [Graphics:Images/CauchyRiemannModHome_gr_493.gif].

Solution 9 (a).

See text and/or instructor's solution manual.

Answer.  [Graphics:../Images/CauchyRiemannModHome_gr_494.gif]  and  [Graphics:../Images/CauchyRiemannModHome_gr_495.gif].  

The partials are continuous everywhere, so  f(z)  is entire.

Solution.  [Graphics:../Images/CauchyRiemannModHome_gr_496.gif],    and

                 [Graphics:../Images/CauchyRiemannModHome_gr_497.gif],      [Graphics:../Images/CauchyRiemannModHome_gr_498.gif]    so that  

[Graphics:../Images/CauchyRiemannModHome_gr_499.gif],     [Graphics:../Images/CauchyRiemannModHome_gr_500.gif],     [Graphics:../Images/CauchyRiemannModHome_gr_501.gif],     [Graphics:../Images/CauchyRiemannModHome_gr_502.gif].   

The  Cauchy Riemann equations are  

        [Graphics:../Images/CauchyRiemannModHome_gr_503.gif],  

        [Graphics:../Images/CauchyRiemannModHome_gr_504.gif],

which hold for all  z.

The partials are continuous everywhere, so   

[Graphics:../Images/CauchyRiemannModHome_gr_505.gif][Graphics:../Images/CauchyRiemannModHome_gr_506.gif],  

for all  z.  Therefore,  [Graphics:../Images/CauchyRiemannModHome_gr_507.gif]  is an entire function.

We are done.   

Remark.  Later, in Section 5.4 we will show that  

(5-34)                    [Graphics:../Images/CauchyRiemannModHome_gr_508.gif],
                    and
(5-35)                    [Graphics:../Images/CauchyRiemannModHome_gr_509.gif].  

Then  [Graphics:../Images/CauchyRiemannModHome_gr_510.gif][Graphics:../Images/CauchyRiemannModHome_gr_511.gif]  will be an analytic function and its derivative is

[Graphics:../Images/CauchyRiemannModHome_gr_512.gif][Graphics:../Images/CauchyRiemannModHome_gr_513.gif].  

We are really done.   

Aside.  We can let Mathematica double check our work.

[Graphics:../Images/CauchyRiemannModHome_gr_514.gif]

[Graphics:../Images/CauchyRiemannModHome_gr_515.gif]
[Graphics:../Images/CauchyRiemannModHome_gr_516.gif]

                     [Graphics:../Images/CauchyRiemannModHome_gr_517.gif]          [Graphics:../Images/CauchyRiemannModHome_gr_518.gif]

  

                    The analytic function  [Graphics:../Images/CauchyRiemannModHome_gr_519.gif]  maps this orthogonal grid onto an orthogonal grid.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This solution is complements of the authors.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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