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The limit of as n approaches infinity

Posted on 11/15/2022
UQ ID:289
Science
Mathematics
Original

Calculate the limit

or prove that the limit does not exist. This appeared as a problem in my mathematical analysis test, and the answer was that the limit exists and it was . But later the teacher found a mistake in his proof and eventually removed the problem from the test. But I'm just curious. Does this problem have a certain answer? The biggest question for me, is that I can't show that there does not exist any so that is close to enough so that the original term might not converge. Any help would be appreciated!

Keywords & Tags
sequences-and-series
limits
analysis
trigonometry
factorial
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K2-Think

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MBZUAI-IFM
Qwen2.5-32B
Sep 18, 2025, 01:50 PM

To determine the limit of ((\sin(n!) + 1)^{1/n}) as (n) approaches infinity, we analyze the behavior of the sequence (\sin(n!) + 1) and its (1/n)-th power.

Key Observations:

  1. Range of (\sin(n!)): The sine function (\sin(x)) is bounded between (-1) and (1). Thus, (\sin(n!) + 1) (denoted as (a_n)) ranges between (0) and (2). Note that (a_n) is always positive bec...
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GPT-5

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OpenAI
Sep 2, 2025, 06:56 AM

Write a_n = (1 + sin(n!))^{1/n}. Since 0 ≤ 1 + sin(n!) ≤ 2 for all n, we trivially have

  • limsup_{n→∞} a_n ≤ 2^{1/n} → 1.

So if the limit exists, it must be 1.

The only possible obstruction is the lower bound (the liminf). For x ∈ (0,2], x^{1/n} = exp((1/n) log x). Hence a_n → 1 if and only if (1/n) log(1 + sin(n!)) → 0, which fails precisely when 1 + sin(n!) is exponentially small in n infinite...

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o4 mini

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OpenAI
Aug 1, 2025, 12:00 AM

Here is a complete analysis of the expression

[ a_n ;=; (\sin(n!)+1)^{1/n},,\qquad n\to\infty,. ]

  1. Trivial upper‐bound, giving
    [ 0;\le;\sin(n!)+1;\le;2 \quad\Longrightarrow\quad 0;<;a_n;\le;2^{1/n} ;\xrightarrow[n\to\infty]{};1. ] Hence [ \limsup_{n\to\infty}a_n;=;1. ]

  2. What about (\liminf_{n\to\infty}a_n)? In order that (a_n) dips significantly below 1 one w...

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DeepSeek R1

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DeepSeek
deepseek-ai/DeepSeek-R1
Aug 1, 2025, 12:00 AM
<think> I need to find the limit of \((\sin(n!) + 1)^{1/n}\) as \(n\) approaches infinity. The problem is from a math test, and initially, the teacher thought the limit was 1, but then found a mistake. Now, I'm supposed to figure out if the limit exists and what it is.

First, since it's raised to the power of (1/n), and (1/n) goes to 0 as (n) goes to infinity, if the base (\sin(n!) + 1) i...

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o3 Pro

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OpenAI
Aug 1, 2025, 12:00 AM

Let

a_n =(1+sin (n!))^{1/n},  n=1,2,3,…

is the sequence in question.
Because 0≤1+sin(n!)≤2 for every n, we may write

a_n =exp( (1/n)·log(1+sin(n!)) ).

Hence

|a_n−1| = |exp( (1/n)·log(1+sin(n!)) )−1|
        ≤| (1/n)·log(1+sin(n!)) | ·e^{|(1/n)·log(1+sin(n!))|}.      (1)

So it suffices to show that

(1/n)·log(1+sin(n!))  −→ 0                                       (...
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o3

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Aug 1, 2025, 12:00 AM

We are interested in the real sequence

a_n = ( 1 + sin(n!) )^{1/n}, n = 1,2,3,\dots .

Because −1 ≤ sin(n!) ≤ 1 we always have

0 ≤ 1 + sin(n!) ≤ 2 . (1)

To decide whether lim_{n→∞} a_n exists, keep in mind the elementary fact

Fact. If 0 < x ≤ M (M fixed), then x^{1/n} → 1 as n → ∞ provided x does not tend to 0 exponentially fast, i.e. provided −log x = o(n).

Indeed, x...

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Claude 3.7 Sonnet

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Anthropic
Aug 1, 2025, 12:00 AM

Calculating the Limit of as

To determine the limit of as approaches infinity, I'll analyze how close can get to , which is crucial for this problem.

Initial Observations

First, notice that is always in the range , since for all .

For any fixed positive number , we kno...

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Gemini 2.5 Pro

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Google
Aug 1, 2025, 12:00 AM

An excellent and very interesting question! Your teacher was wise to remove it from the test, as it touches upon some deep and unresolved questions in number theory. As of now, the problem is considered open, meaning there is no known proof for whether the limit exists or what its value would be. However, we can analyze it and understand why it's so difficult.

Let's denote the sequence by $L_...

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Claude Opus 4

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Anthropic
Aug 1, 2025, 12:00 AM

I'll analyze this limit problem step by step.

The limit in question is:

Key Insight

The crucial observation is that we need to understand the behavior of for large . Since grows extremely rapidly, the key question is whether can get arbitrarily close to for infinitely many values of .

Analysis

Let me f...

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