Prove Set of Real Numbers Unbounded: Tips & Examples

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In summary, to prove that a set of real numbers is unbounded, one can show that the cardinality of the set exceeds ℵ and is therefore uncountable. This can be accomplished by establishing that the set has no limit or by using Georg Cantor's diagonalization process. The definition of "bounded" is essential in determining the direction of the proof.
  • #1
xlalcciax
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How to prove that set of real numbers is unbounded?
 
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  • #2
What is your definition of unbounded?
 
  • #3
xlalcciax said:
How to prove that set of real numbers is unbounded?

It most likely involves showing that the cardinality of the real numbers exceeds ℵ ("aleph null").
 
  • #4
reef said:
It most likely involves showing that the cardinality of the real numbers exceeds ℵ ("aleph null").
That would be "uncountable". "Unbounded" has a bunch of different but equivalent definitions, like "is not a subset of some open ball".
 
  • #5
True. I figured that you would have to go about it the same type of way. Do you have to establish that a set without bound has no limit? Regardless, I'd be interested to see the proof when xlalcciax figures it out.
 
  • #6
It's much easier to prove that ℝ is unbounded than to prove that ℝ is uncountable. Once you've written down a definition of "bounded" and thought about what it means, you're pretty much done.
 
  • #7
I wish xlalcciax would get back to us with his definition of "bounded" so we would know in which direction to go.
 
  • #8
You could be really lazy and just say that the real numbers can be proven to be uncountable by means of Georg Cantors diagonalization process.. lol.
 

Related to Prove Set of Real Numbers Unbounded: Tips & Examples

1. What does it mean for a set of real numbers to be unbounded?

A set of real numbers is considered unbounded if there is no upper or lower limit to the numbers in the set. This means that the set can contain infinitely large or infinitely small values.

2. How can I prove that a set of real numbers is unbounded?

To prove that a set of real numbers is unbounded, you can show that there is no finite upper or lower bound for the numbers in the set. This can be done by finding a sequence of numbers within the set that continue to increase or decrease without ever reaching an endpoint.

3. What are some tips for proving that a set of real numbers is unbounded?

One tip is to look for patterns within the set of numbers. If you notice that the numbers are getting larger or smaller with each consecutive value, this can be a strong indication that the set is unbounded. Another tip is to use mathematical induction, which can help show that there is no upper or lower bound for the numbers in the set.

4. Can you provide an example of proving a set of real numbers is unbounded?

Sure, let's say we have the set of numbers {1, 2, 3, 4, ...}. We can see that this set continues to increase without ever reaching an endpoint, thus making it unbounded. Another example could be the set {-1, -2, -3, -4, ...}, which continues to decrease without ever reaching an endpoint.

5. Are there any real-life applications of proving a set of real numbers is unbounded?

Yes, there are many real-life applications of understanding and proving unbounded sets of real numbers. For example, in economics, knowledge of unbounded sets can help predict the behavior of markets and investments. In physics, unbounded sets can be used to model infinite systems such as the behavior of particles in space.

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