What Are the Interior, Boundary, Closure, and Accumulation Points of These Sets?

Click For Summary

Discussion Overview

The discussion revolves around identifying the interior, boundary, closure, and accumulation points of specific sets defined by participants. The sets include combinations of rational and irrational numbers, as well as geometric representations in R^n. The conversation includes theoretical aspects and clarifications related to these concepts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Participant 1 presents three sets and expresses confusion about their properties, particularly for parts a and b.
  • Participant 2 questions the definition of L in part c and emphasizes the importance of knowing that between any two irrational numbers, there exists a rational number.
  • Participant 3 agrees with Participant 1's conclusion for part c and suggests drawing pictures to aid understanding. They prompt further exploration of the sets in parts a and b, questioning the boundedness of set A.
  • Participant 3 provides hints regarding accumulation points for part a, suggesting to consider sequences approaching 2 and how they relate to the set.
  • Participant 5 reiterates the interpretation of part b and questions the meaningfulness of the set as initially described, proposing a clearer definition.
  • Participant 6 confirms their intended meaning regarding part b after clarification from Participant 5.

Areas of Agreement / Disagreement

There is no consensus on the properties of the sets in parts a and b, as participants express differing interpretations and seek clarification. The discussion remains unresolved regarding the correct identification of interior, boundary, closure, and accumulation points for the sets presented.

Contextual Notes

Participants note the importance of definitions and the need for clarity in the descriptions of the sets, particularly regarding the nature of irrational numbers and their relationship to rational numbers. There is an acknowledgment of potential confusion stemming from the initial statements.

ShengyaoLiang
Messages
23
Reaction score
0
a. 1/n + 1/m : m and n are both in N
b. x in irrational #s : x ≤ root 2 ∪ N
c. the straight line L through 2points a and b in R^n.


for part c. i got: intA= empty ; bdA=clA=accA=L Is this correct? how about part a and part b...i am so confused...
 
Last edited:
Physics news on Phys.org
As far as the first is concerned I don't know because you didn't say what L is! For (b) you need to know that "between any two irrational numbers, there is at least one rational number". (c) should be easy using the definition of "neighborhood". What does a neighborhood in Rn look like?
 
your c) looks correct.

draw pictures. it will help get rid of the confusion. what textbook are you using for this class?

now for a) and b) determine the sets. Is set A) bounded?

Hint for a's accumulation points, how many points come "near" 2? how about ANY number of the form 1+1/m in between 1 and 2? Fix n=1, let m=1,2,3..., what happens? Fix n as N (N is any fixed integer) and let 1/N +1/m with m=1,2,3... what happens? All these sequences I have suggested are contained in the set A.

for b) do you mean all irrational numbers that are less than the root of 2 and all irrationals that are natural numbers?

edit: werever i say integer, i mean positive integer!
 
don't have a formal texeboot for analysis1, only have a courseware...

thanks a lot.
 
SiddharthM said:
your c) looks correct.
for b) do you mean all irrational numbers that are less than the root of 2 and all irrationals that are natural numbers?

That would make the second part pretty meaningless!

I would interpret it as b. {x in irrational #s : x ≤ root 2} ∪ N
 
sorry yes, that is actually what i meant to ask.
 

Similar threads

Replies
11
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 19 ·
Replies
19
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K