Exercise 1.  Find the following limits.

1 (a).  [Graphics:Images/ComplexSequenceSeriesModHome_gr_1.gif].

Solution 1 (a).

See text and/or instructor's solution manual.

Answer   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_2.gif].

Solution.  Method I.  We have  

            [Graphics:../Images/ComplexSequenceSeriesModHome_gr_3.gif]  

We can use the "squeeze theorem" for real sequences to show that both  [Graphics:../Images/ComplexSequenceSeriesModHome_gr_4.gif]  and  [Graphics:../Images/ComplexSequenceSeriesModHome_gr_5.gif]  converge to  0.

                    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_6.gif],   and

                    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_7.gif],  

Hence we have,   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_8.gif]    and    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_9.gif].

Therefore   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_10.gif].

Solution.  Method II.  Use the fact that   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_11.gif]   iff   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_12.gif].    (You will be asked to prove this fact in Exercise 17.)

Find the limit of the sequence of absolute values:


                    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_13.gif]  

Then,    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_14.gif]   implies that    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_15.gif].

We are done.   

Aside.  We can let Mathematica double check our work.

[Graphics:../Images/ComplexSequenceSeriesModHome_gr_16.gif]

[Graphics:../Images/ComplexSequenceSeriesModHome_gr_17.gif]


[Graphics:../Images/ComplexSequenceSeriesModHome_gr_18.gif]

[Graphics:../Images/ComplexSequenceSeriesModHome_gr_19.gif]


[Graphics:../Images/ComplexSequenceSeriesModHome_gr_20.gif]

[Graphics:../Images/ComplexSequenceSeriesModHome_gr_21.gif]


                    [Graphics:../Images/ComplexSequenceSeriesModHome_gr_22.gif]

                    The graph of   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_23.gif],   and the limit point   [Graphics:../Images/ComplexSequenceSeriesModHome_gr_24.gif].  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This solution is complements of the authors.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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