Topology of real number

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In summary, the conversation discusses the set P={1/n:n is counting number} and whether it is equal to (0,1]. It is clarified that P contains only rational numbers and thus is not equal to (0,1]. The possibility of a set not containing both interior and boundary points is also raised, with the example of an open set in a metric space provided.
  • #1
kimkibun
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consider the set P={1/n:n is counting number}, my classmate said that P is equal to (0,1] but actually i don't agree with him since (0,1] contains irrational numbers. is he correct? also, is it possible for a set not to contain both interior and boundary points?
 
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  • #2
Can you elaborate? You're correct, of course, that P = {1/n:n is counting number} contains only rational numbers (and not even all of the rational numbers in the unit interval), and so is not equal to (0,1], but maybe he meant something other than equality of sets?

As for your second question: Are you asking if there exists a set that fails to contain both interior an boundary points? In an open set in a metric space, by definition, all points are interior points, so we could take any open ball, for example: every point is interior, and there are no boundary points.
 

What is the topology of real numbers?

The topology of real numbers is the mathematical study of the properties and relationships of the real numbers, including their open and closed sets, continuity, and convergence.

What are open and closed sets in the topology of real numbers?

In the topology of real numbers, an open set is a set that does not contain its boundary points, while a closed set is a set that contains all of its boundary points.

What is continuity in the topology of real numbers?

In the topology of real numbers, continuity refers to the property of a function where small changes in the input result in small changes in the output. In other words, a function is continuous if its graph can be drawn without lifting the pen.

What is convergence in the topology of real numbers?

In the topology of real numbers, convergence refers to the property of a sequence of numbers that approaches a specific limit as the number of terms increases. For example, the sequence 1, 1/2, 1/3, 1/4, ... converges to 0 as the number of terms increases.

How is the topology of real numbers used in other areas of mathematics?

The topology of real numbers is a fundamental concept in mathematics and has applications in various fields including analysis, geometry, and algebra. It is also used in physics and engineering to model continuous systems and in computer science for data analysis and optimization.

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