Defining Closed, Open, and Compact Sets in R^n

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SUMMARY

This discussion focuses on defining closed, open, and compact sets in R^n, specifically under the standard Euclidean metric. The set defined by the inequality {x, y: 1 < x < 2} is identified as an open set because every point within it has an open ball that remains within the set. The discussion emphasizes the importance of specifying the topology when analyzing these properties, particularly noting that the topologies induced by the standard Euclidean metric align with the product topology in R^n.

PREREQUISITES
  • Understanding of Euclidean space R^n
  • Familiarity with basic topology concepts
  • Knowledge of open and closed sets
  • Ability to work with inequalities in mathematical sets
NEXT STEPS
  • Study the definitions and properties of compact sets in R^n
  • Learn about the concept of metric topology in detail
  • Explore the relationship between open balls and open sets
  • Investigate examples of closed sets in R^2 and R^3
USEFUL FOR

Mathematics students, particularly those studying topology and real analysis, as well as educators looking to clarify concepts of open and closed sets in Euclidean spaces.

Garcher
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Homework Statement



How to define closed,, open and compact sets?Are they bounded or not?

Homework Equations



For example {x,y:1<x<2}


The Attempt at a Solution



It's is opened as all points are inner

Can you please say the rule for defining the type of the set? Like for example 1<=(x^2+y^2)<=2?
 
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You are talking about sets in R^2. In general, before considering topological properties, you first have to specify the topology you're considering. In R^n, the topologies induced by the standard euclidean metric are the same as the product topology. So, I'll assume you're given the standard euclidean metric and looking at it's corresponding metric topology.

Your first set is open, since for any point in the set you can find an open ball around that point belonging to the set. Can you do this for the second set?
 

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