Example 4.23.  The infinite series  [Graphics:Images/ComplexPowerSeriesMod_gr_97.gif]  has radius of convergence [Graphics:Images/ComplexPowerSeriesMod_gr_98.gif] by the ratio test because

            [Graphics:Images/ComplexPowerSeriesMod_gr_99.gif].

Since the limit equals  0,  we set  [Graphics:Images/ComplexPowerSeriesMod_gr_100.gif].    

Explore Solution 4.23.

Enter the formula for the coefficients.

[Graphics:../Images/ComplexPowerSeriesMod_gr_101.gif]




[Graphics:../Images/ComplexPowerSeriesMod_gr_102.gif]

 

 

 

Use d'Alembert's ratio test and find the limit and then the radius of convergence R.

[Graphics:../Images/ComplexPowerSeriesMod_gr_103.gif]




[Graphics:../Images/ComplexPowerSeriesMod_gr_104.gif]

 

 

 

The sum of the series is a well known function.

[Graphics:../Images/ComplexPowerSeriesMod_gr_105.gif]



[Graphics:../Images/ComplexPowerSeriesMod_gr_106.gif]

 

 

 

We can plot some of the partial sums and see that they converge to f[z].

[Graphics:../Images/ComplexPowerSeriesMod_gr_107.gif]





[Graphics:../Images/ComplexPowerSeriesMod_gr_108.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_109.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_110.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_111.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_112.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_113.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_114.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_115.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_116.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_117.gif]





[Graphics:../Images/ComplexPowerSeriesMod_gr_118.gif]





[Graphics:../Images/ComplexPowerSeriesMod_gr_119.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_120.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_121.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_122.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_123.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_124.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_125.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_126.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_127.gif]

[Graphics:../Images/ComplexPowerSeriesMod_gr_128.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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