Determine if the given set is Bounded- Complex Numbers

chwala
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Homework Statement
See attached.
Relevant Equations
Complex Numbers
My interest is only on part (a). Wah! been going round circles to try understand why the radius = ##2##. I know that the given sequence is both bounded and monotonic. I can state that its bounded above by ##1## and bounded below by ##0##. Now when it comes to the radius=##2##, i can also say that the boundary of set ##S## also consists/ includes the complement of the set and that will gives us;##r^2=\sqrt{(1--1)^2+(0-0)^2}=\sqrt{4}##
##r=2.##

I hope this is the correct reasoning, otherwise i need your insight...i also tried looking at the cauchy criterion,... among other...

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Say s is a member of S other than i , as ##|s| < 1## s is inside unit circle of complex plane on which i is. Both s and i are inside the circle |z|=2.

Not only |z|##\leq##2 but other regions including S inside work, e.g. |z|##\leq##3/2, |z|##\leq##3,
the rectangle region of ## 0 \leq I am \ z \leq 1+\epsilon_1, |Re\ z| \leq \epsilon_2 ## where ##0<\epsilon_1,\epsilon_2##.
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anuttarasammyak said:
Say s is a member of S other than i , as ##|s| < 1## s is inside unit circle of complex plane on which i is. Both s and i are inside the circle |z|=2.

Not only |z|##\leq##2 but other regions including S inside work, e.g. |z|##\leq##3/2, |z|##\leq##3,
the rectangle region of ## 0 \leq I am \ z \leq 1+\epsilon_1, |Re\ z| \leq \epsilon_2 ## where ##0<\epsilon_1,\epsilon_2##.
View attachment 316045
Something am not getting here, I guess I need to check...I thought the set members are bound by ##1## and ##0##. You have ##1.5## which clearly in my understanding is not part of set S. My understanding of radius here is the distance between i.e neighbourhood of set ##S## and ##S^{'}##.
 
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chwala said:
You have 1.5 which clearly in my understanding is not part of set S.
You are right. Even as for the answer in the textbook, z=1 belongs to |z|<2, but it does not belong to set S.

Say T is a set, e.g. |z| ##\leq## 2, |z| ##\leq \sqrt{2}##, |z| ##\leq \pi##, |z| ##\leq 3/2## ... any circle larger than unit circle in complex plane,
##S \subset T##
Set T is not part of set S. Set S is part of set T.
 
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There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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