The limit of as n approaches infinity
The limit of
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
K2-Think
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:
- 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...
GPT-5
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...
o4 mini
Here is a complete analysis of the expression
[ a_n ;=; (\sin(n!)+1)^{1/n},,\qquad n\to\infty,. ]
-
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. ] -
What about (\liminf_{n\to\infty}a_n)? In order that (a_n) dips significantly below 1 one w...
DeepSeek R1
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...
o3 Pro
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 (...
o3
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...
Claude 3.7 Sonnet
Calculating the Limit of as
To determine the limit of
Initial Observations
First, notice that
For any fixed positive number
Gemini 2.5 Pro
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_...
Claude Opus 4
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
Analysis
Let me f...
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