Limit of a sequence does not goes to zero

In summary, the conversation discusses verifying a proof that shows a limit with a particular property does not go to 0. The proof uses the fact that if |a_n|<|a_{n+1}| for a sequence, then the limit cannot be 0. The proof is verified and the person is happy to have discovered this on their own.
  • #1
Seydlitz
263
4

Homework Statement


Could you guys please verify this proof of mine? I want to show that a limit with particular property does not go to 0. It is part of the proof that when a sequence have an ever increasing term then the limit of the sequence is not 0.

The Attempt at a Solution



The ##\lim_{n \to \infty} a_n \neq 0## if ##|a_n|<|a_{n+1}|##

Suppose ##\lim_{n \to \infty} a_n = 0##, then there exist ##n>0##, such that ##|a_N| < \epsilon## when ##N>n##. Taking an arbitrary ##a_n## as ##\epsilon##, we can get ##|a_N| < |a_n|.## Because it also true that ##N=n+1>n##, we get ##|a_n|>|a_{n+1}|##. A contradiction.

Hence it is not possible for the limit to be 0.

Thank You
 
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  • #2
Seydlitz said:

Homework Statement


Could you guys please verify this proof of mine? I want to show that a limit with particular property does not go to 0. It is part of the proof that when a sequence have an ever increasing term then the limit of the sequence is not 0.

The Attempt at a Solution



The ##\lim_{n \to \infty} a_n \neq 0## if ##|a_n|<|a_{n+1}|##

Suppose ##\lim_{n \to \infty} a_n = 0##, then there exist ##n>0##, such that ##|a_N| < \epsilon## when ##N>n##. Taking an arbitrary ##a_n## as ##\epsilon##, we can get ##|a_N| < |a_n|.## Because it also true that ##N=n+1>n##, we get ##|a_n|>|a_{n+1}|##. A contradiction.

Hence it is not possible for the limit to be 0.

Thank You

That looks just fine to me.
 
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  • #3
Ok thanks for your verification Dick! I'm quite happy to discover this by myself.
 

Related to Limit of a sequence does not goes to zero

1. What does it mean when the limit of a sequence does not go to zero?

When the limit of a sequence does not go to zero, it means that the values in the sequence do not approach zero as the number of terms in the sequence increases. This can also be interpreted as the sequence having a non-zero limit.

2. Can a sequence have a limit that is not equal to zero?

Yes, a sequence can have a limit that is not equal to zero. This means that as the number of terms in the sequence increases, the values of the sequence approach a specific value that is not equal to zero.

3. How can you determine if the limit of a sequence does not go to zero?

To determine if the limit of a sequence does not go to zero, you can evaluate the limit of the sequence using various mathematical techniques such as the squeeze theorem or the ratio test. If the limit is not equal to zero, then the sequence does not go to zero.

4. What are some examples of sequences with limits that do not go to zero?

Examples of sequences with limits that do not go to zero include the harmonic series, the alternating harmonic series, and the geometric series with a common ratio greater than 1. These sequences have limits that are finite and non-zero values.

5. Why is it important to understand when the limit of a sequence does not go to zero?

Understanding when the limit of a sequence does not go to zero is important in various areas of mathematics, such as calculus and real analysis. It allows us to determine the behavior of a sequence and its limit, which can be useful in solving problems and proving theorems.

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