What Defines a Ball, Interior, and Limit Point in Metric Spaces?

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SUMMARY

This discussion focuses on defining key concepts in metric spaces, specifically the ball B(p,r), interior points, and limit points. The ball is defined as B(p,r) = {xεX: d(x,p) ≤ r}, indicating a closed ball around point p with radius r. An interior point of a set E is defined as a point p such that there exists a ball B(p,r) entirely contained in E. A limit point of E is a point p where every neighborhood of p contains at least one point from E distinct from p itself. Clarifications on these definitions are essential for understanding metric spaces.

PREREQUISITES
  • Understanding of metric spaces and their properties
  • Familiarity with the concept of distance functions in mathematics
  • Knowledge of closed and open sets
  • Basic comprehension of neighborhood definitions in topology
NEXT STEPS
  • Research the formal definitions of interior points and limit points in metric spaces
  • Study the differences between open and closed balls in metric spaces
  • Explore the implications of limit points in convergence and continuity
  • Examine examples of metric spaces to solidify understanding of these concepts
USEFUL FOR

Students of mathematics, particularly those studying topology or real analysis, as well as educators seeking to clarify foundational concepts in metric spaces.

teme92
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Homework Statement



For a metric space (X,d) and a subset E of X, de fine each of the terms:

(i) the ball B(p,r), where pεX and r > 0
(ii) p is an interior point of E
(iii) p is a limit point of E


Homework Equations





The Attempt at a Solution



i) Br(p) = {xεX: d(x.p)≤r}


ii) Br(p) = {xεX: d(x.p)≥r}

iii) I do not know the answer to this at all.

I do not know if the first two parts are correct either so I would appreciate any help given.
 
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teme92 said:

Homework Statement



For a metric space (X,d) and a subset E of X, define each of the terms:

(i) the ball B(p,r), where pεX and r > 0
(ii) p is an interior point of E
(iii) p is a limit point of E


Homework Equations





The Attempt at a Solution



i) Br(p) = {xεX: d(x.p)≤r}


ii) Br(p) = {xεX: d(x.p)≥r}

iii) I do not know the answer to this at all.

I do not know if the first two parts are correct either so I would appreciate any help given.

i) might be ok, if you mean 'closed ball' and d(x.p) should be d(x,p). But seriously, these are definitions. If you don't know what 'interior' or 'limit point' mean you should look them up. The process of looking them up will give you the definitions.
 
ok thanks guys for the help :)
 

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