Is this sequence divergent or convergent?

In summary, the question is whether the sequence {4+sin(1/2*pi*n)} converges or diverges, and if it converges, what is the limit? The conversation discusses how sin oscillates between 1 and -1, and whether this means the limit does not exist. It is determined that the sequence takes three values (3, 4, and 5) and therefore, only one limit can exist. It is concluded that the limit does not exist, as the sequence oscillates between the three values.
  • #1
Sarah Kenney
10
1

Homework Statement


I'm trying to find out whether or not this sequence diverges or converges. If it converges, then what's the limit.
{4+sin(1/2*pi*n)}

The Attempt at a Solution


This one is a bit confusing to me since sin oscillates between 1 and -1. So if you plug in (pi*infinity)/2, that would go back and forth. So does that mean that the limit does not exist?

Thanks in advance.
 
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  • #2
Sarah Kenney said:

Homework Statement


I'm trying to find out whether or not this sequence diverges or converges. If it converges, then what's the limit.
{4+sin(1/2*pi*n)}

The Attempt at a Solution


This one is a bit confusing to me since sin oscillates between 1 and -1. So if you plug in (pi*infinity)/2, that would go back and forth. So does that mean that the limit does not exist?

Thanks in advance.

If the limit does exist, what could it be?
 
  • #3
PeroK said:
If the limit does exist, what could it be?

Would the limit be 5 since sin(pi\2) is 1?
 
  • #4
Sarah Kenney said:
Would the limit be 5 since sin(pi\2) is 1?

How many different values does the sequence have?
 
  • #5
Oh, so because it oscillates between -1 and 1, then the limit is from 3 to 5?
 
  • #6
Sarah Kenney said:
Oh, so because it oscillates between -1 and 1, then the limit is from 3 to 5?

You can only have one limit (at most)! The sequence takes only three values: 3, 4 and 5. Do you just have to work out what the limit is (if it exists), or do you have to prove it?
 
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  • #7
Sarah Kenney said:

Homework Statement


I'm trying to find out whether or not this sequence diverges or converges. If it converges, then what's the limit.
{4+sin(1/2*pi*n)}

The Attempt at a Solution


This one is a bit confusing to me since sin oscillates between 1 and -1. So if you plug in (pi*infinity)/2, that would go back and forth. So does that mean that the limit does not exist?

Thanks in advance.

You need to review the basics: what is the definition of a limit? Does your sequence have the required properties?
 
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Likes Sarah Kenney
  • #8
Ok, I think I've got it. It does not exist, since the sequence oscillates between 5, 4, and 3. Thanks!
 

1. What is the difference between a divergent and convergent sequence?

A divergent sequence is one whose terms increase or decrease without limit as you move further along the sequence. A convergent sequence, on the other hand, approaches a specific value or limit as you move further along the sequence.

2. How can I determine if a sequence is divergent or convergent?

To determine if a sequence is divergent or convergent, you can use different tests such as the divergence test, the comparison test, the ratio test, or the root test. These tests involve analyzing the behavior of the sequence's terms as you move further along the sequence.

3. What is the importance of knowing if a sequence is divergent or convergent?

The behavior of a sequence can provide valuable information about the behavior of a function, especially near its limit. Knowing if a sequence is divergent or convergent can help in understanding the convergence or divergence of a series, which is used in various mathematical and scientific applications.

4. Can a sequence be both divergent and convergent?

No, a sequence cannot be both divergent and convergent. A sequence must either approach a specific value or increase/decrease without limit as you move further along the sequence. It cannot exhibit both behaviors simultaneously.

5. Are there any real-life applications of divergent and convergent sequences?

Yes, divergent and convergent sequences are used in various fields such as physics, engineering, and finance. For example, in physics, the behavior of a sequence can help in understanding the motion of an object as it approaches a specific limit. In finance, the convergence or divergence of a sequence is used in calculating compound interest and determining the stability of investment portfolios.

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