For questions related to Euler's constant $\gamma$, which is defined to be the limiting difference between the natural logarithm and the harmonic series.

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5
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4answers
121 views

How do we show that $\ln{2}-\gamma=\sum_{n=1}^{\infty}{\zeta(2n+1)\over 2^{2n}(2n+1)}?$

$$\ln{2}-\gamma=\sum_{n=1}^{\infty}{\zeta(2n+1)\over 2^{2n}(2n+1)}\tag1$$ Any hints?
0
votes
2answers
54 views

Natural log operation on $e^{i \tau}$ [duplicate]

I have a layman's question: $e^{i\pi} = -1$ ... euler's identity and $e^{i\tau}$ = 1 where $\tau = 2\pi$ so if I assume that $e^x=y$ implies $ln(y)=x$, which it should, then $ln(1) = i\tau$ but $...
4
votes
2answers
115 views

Any integral or series to prove $\frac{1}{\sqrt{3}}>\gamma$?

I recently noticed that these two numbers are remarkably close: $$\frac{1}{\sqrt{3}}-\gamma=0.000135\dots$$ Are there any integrals or series which can prove that $\frac{1}{\sqrt{3}}>\gamma$? ...
4
votes
1answer
55 views

How to prove this continued fraction connection between $\gamma$ and $e$?

There is apparently a curious connection between Euler-Mascheroni constant $\gamma$ and $e$ in the form of an infinite series and continued fraction: $$e \gamma=e \sum_{n=1}^{\infty} \frac{(-1)^{n+1}}...
1
vote
1answer
64 views

Implicit Euler method and explicit Euler method

I wanna know what is the difference between explicit Euler's method and implicit Euler's method. And is the local truncation error for both of them is $O(h)$ and the coefficient of the $O(h)$ term is $...
5
votes
2answers
90 views

Characterizations of $e^x$

I've been thinking about the following problem for a while: (AFAIK) the 'exponential function', $e^x$ can be characterized as the unique solution to the following differential equation with initial ...
0
votes
1answer
25 views

Deduction of 2nd order ODE general solutions

When I have some ODE, for example: $$ u''(t) + 5u(t) = 0 $$ I put together a characteristic equation: $$ \lambda ^2 + 5 = 0 $$ Then I compute its roots $r_1$ and $r_2$. And now there are some ...
0
votes
2answers
40 views

How can an imaginary equation give a real answer?

I came across this equation, $$ e^{ix} = \cos(x) + i\sin(x) $$ This is the simplified version, the real one is more complex but this part is the one I have a question about. The right side clearly has ...
0
votes
3answers
36 views

Is there a non-exponential function whose limit at infinity is a real, irrational number?

$e$, for example, can be calculated through a non-polynomial function $(1+1/x)^x$, but I cant think of an example for a non-exponential function (or rational function) where the limit to infinity ...
2
votes
0answers
41 views

Representation of e

I was on this wikipedia page https://en.wikipedia.org/wiki/List_of_representations_of_e which has a list of representations of the constant e. I came across this one representation that looked ...
0
votes
1answer
18 views

Graph $S$ and its image $f(S)$

$$S=\{z: -1<Re(z)<2\}$$ $$w=f(z)=e^z$$ Graph $S$ and $f(S)= \{w\}=\{f(z)\mid z \in S\}$ My attempt: This is what I think it should look like. Correct me if I'm wrong, but I think the general ...
2
votes
1answer
31 views

Approximating end behavior of a function by plugging in infinity

In Algebra 2, I learned to be able to tell if the end behavior of a function has an asymptote, approaches infinity, approaches zero, etc, by plugging in numbers closer and closer to infinity, or by ...
0
votes
0answers
26 views

Different Type of Euler's Circuit and Path (Different Looking Graph)

So I have become familiar with the basic graphs that have dots, and lines connection dot to dot. I know that a Euler's circuit is touching every edge of a graph once, and returning to the same point, ...
3
votes
2answers
110 views

How to prove this limit about $\gamma=\lim_{N\to \infty }\left(\sum_{n=1}^N\frac{1}{n}-\ln N\right)$

I have no idea how to prove it. $$\lim_{m\rightarrow \infty }\left [ -\frac{1}{2m}+\ln\left ( \frac{e}{m} \right )+\sum_{n=2}^{m}\left ( \frac{1}{n}-\frac{\zeta \left ( 1-n \right )}{m^{n}} \right ) \...
1
vote
2answers
60 views

Where can I find a proof for $\lim\limits_{n \to \infty} \left (n - \Gamma \left( \frac 1n \right) \right) = \gamma$?

I found in a book the following limit: $\lim\limits_{n \to \infty} \left (n - \Gamma \left( \frac 1n \right) \right) = \gamma$. They say that a proof for this is in "Havil, J.: GAMMA, Exploring Euler’...
2
votes
2answers
145 views

Proving $\lim_{n\to\infty}\sum_{k=n}^{\infty}\Big(\frac{1}{n\left\lfloor\frac kn\right\rfloor}-\frac1k\Big)=\gamma$

I remember arriving at the following equality: $$\lim_{n\to\infty}\sum_{k=n}^{\infty}\left(\frac{1}{n\left\lfloor\frac kn\right\rfloor}-\frac1k\right)=\gamma$$ where $\gamma$ denotes the Euler-...
1
vote
1answer
59 views

When can I assume $\operatorname{Log}$ means the natural log?

I have a problem that says: Express $e^{\operatorname{Log}(3+4i)}$ in the form $x+iy$. However, in class we usually only deal with natural log (this problem is from a textbook). How do I know when I ...
4
votes
1answer
85 views

How to prove this series: $\displaystyle \sum_{n=1}^{\infty }\frac{\left ( -1 \right )^{n}\ln n}{n}=\gamma \ln 2-\frac{1}{2}\ln^22$ [duplicate]

How to prove this series $$\sum_{n=1}^{\infty }\frac{\left ( -1 \right )^{n}\ln n}{n}=\gamma \ln 2-\frac{1}{2}\ln^22$$ and \begin{align*} \sum_{n=1}^{\infty }\frac{\left ( -1 \right )^{n}\ln \left ( n+...
1
vote
0answers
79 views

Series for Stieltjes constants from $\gamma= \sum_{n=1}^\infty \left(\frac{2}{n}-\sum_{j=n(n-1)+1}^{n(n+1)} \frac{1}{j}\right)$

Euler's constant has the following representations (Euler-Mascheroni constant expression, further simplification, http://math.stackexchange.com/a/129808/134791, Question on Macys formula for Euler-...
2
votes
1answer
320 views

Why is $e$ close to $H_8$, closer to $H_8\left(1+\frac{1}{80^2}\right)$ and even closer to $\gamma+log\left(\frac{17}{2}\right) +\frac{1}{10^3}$?

The eighth harmonic number happens to be close to $e$. $$e\approx2.71(8)$$ $$H_8=\sum_{k=1}^8 \frac{1}{k}=\frac{761}{280}\approx2.71(7)$$ This leads to the almost-integer $$\frac{e}{H_8}\approx1....
3
votes
1answer
89 views

Why Can my Phone Calculator do $e^{\pi\sqrt{-1}}$ but not $\sqrt{-1}$?

When I type in the identity $e^{\pi\sqrt{-1}}$ on my phone calculator (LG phone running Android), I get the correct result of $-1$ However, when I simply type $\sqrt{-1}$, it returns an error. Why ...
4
votes
1answer
128 views

What is known about the 'Double log Eulers constant', $\lim_{n \to \infty}{\sum_{k=2}^n\frac{1}{k\ln{k}}-\ln\ln{n}}$?

The Euler constant is defined as $$\gamma = \lim_{n \to \infty}{\sum_{k=1}^n\frac{1}{k}-\ln{n}}$$ Let $$q = \lim_{n \to \infty}{\sum_{k=2}^n\frac{1}{k\ln{k}}-\ln\ln{n}}$$ I managed to prove that $$\...
5
votes
4answers
256 views

How fundamental is Euler's identity, really?

Euler's identity, obviously, states that $e^{i \pi} = -1$, deriving from the fact that $e^{ix} = \cos(x) + i \sin(x)$. The trouble I'm having is that that second equation seems to be more of a ...
8
votes
1answer
81 views

Evaluate $\lim_{R\to\infty}\left(\int_0^R\left|\frac{\sin x}{x}\right|dx-\frac{2}{\pi}\log R\right)$

Is there a closed form of $$\lim_{R\to\infty}\left(\int_0^R\left|\frac{\sin x}{x}\right|dx-\frac{2}{\pi}\log R\right)$$ I am pretty interested whether we can find out a closed form of this limit. We ...
0
votes
1answer
28 views

Euler's Method Solving $y' = f(t,y)$: Programming

I'm trying to compute the approximation solution for $$ y' = -2y + 2 - e^{-4t}: 0\le t\le5, y(0) = 1$$ but the answer that I get for $n = 100$ intervals is $-5.069$ which isn't right. What's the issue ...
1
vote
3answers
37 views

Evaluate $\lim\limits_{n\rightarrow\infty}\left(\frac{n^2 + 1}{n^2 - 2}\right)^{n^2}$

$$\lim\limits_{n\rightarrow\infty}\left(\frac{n^2 + 1}{n^2 - 2}\right)^{n^2}$$ Trying to solve this. At first thought it was $1$, but in wolfram it's $e^3$. Thanks
1
vote
3answers
28 views

Absolute value of a complex number with a arbitrary basis

I want to calculate the square of the absolute value of a complex number $x^{ia}$, with $x$ and $a$ being real while $i$ is the imaginary number: $$\left|x^{ia}\right|^2=?.$$ I have trouble because ...
0
votes
1answer
38 views

Limit of exponential function (Eulers number)

I'm struggling with this assignment for a couple of hours, and i dont seem to find any clues :( I have to find the limit of this exponential function: $$\lim_{n \to \infty} (1+\frac{1}{n+2})^{2n+3} $$...
0
votes
0answers
19 views

How to simplify this representation of $\gamma$?

I have a function of two variables, $Z(n,m) = (-1)^m \left( \frac{1}{m-2^n} + \frac{1}{2^n \log (2^n /m)} \right)$, and the infinite sum $\sum_{n=1}^{\infty} \sum_{m=1}^{2^n -1} Z(n,m) = \gamma$, the ...
0
votes
0answers
37 views

Transform cos to e function

What are the steps in order to transform the cosine function to the exponential function: $$ \left[\cos \left(\frac{k \pi} N\right)\right]^n \approx e ^ {\frac{-n}2 \left(\frac{k \pi} N \right)^2} $$...
0
votes
0answers
47 views

Evaluating $\int{e^{-t^{2}}\,dt}$

Let $f(x) = e^{x}$, which, expressed as a Maclaurin series, is equal to: $$\sum_{i = 0}^{\infty}{\frac{x^{i}}{i!}}$$ Therefore, $f(-t^{2})$ gives: $$\sum_{i = 0}^{\infty}{\frac{(-t^{2})^{i}}{i!}} = ...
0
votes
1answer
59 views

Rearrangement of difficult algebraic equations

I have always had difficulty when rearranging large equations of functions to find the roots and also the turning points(using derivatives) and was hoping some people could give me some tips when it ...
1
vote
1answer
65 views

Is the Champernowne constant actually useful

Has the aforementioned constant ever been used in any major proofs? Can it be expressed in terms of $e$, $\pi$, or both? Does it appear in any sort of geometric sense like $\pi$ does? Or is it just a ...
7
votes
1answer
111 views

Integrating:$ \displaystyle \int_0 ^ {\infty}e^{-x^2}\ln(x)dx $

$$ \displaystyle \int_0 ^ {\infty}e^{-x^2}\ln(x)dx = -\frac{1}{4}(\gamma +2\ln(2))\sqrt{\pi} $$ This is a well known integral. But I want to know how to solve it?? Also, please refrain using contour ...
2
votes
1answer
84 views

Is this a valid visualization of Euler's identity as a more generic pattern?

I was reading this nice question about a demonstration of Euler's identity, and tried to visualize how would look the left part of the identity in the complex plane by using the following function: ...
2
votes
1answer
60 views

How can I get $\alpha$ and $\beta$ numerically? (Euler constant)

Let $\gamma_n=\sum_{k=1}^{n}\frac{1}{k}-\ln(n)$ and $\gamma=\lim_{n}\gamma_n$ From the fact $\frac{1}{2(n+1)}\leq\gamma_n-\gamma\leq\frac{1}{2n}$, we have $\gamma_n-\gamma \sim \frac{1}{2n}$ By ...
3
votes
2answers
39 views

How do we bound the function $\frac{-1}{2}\sum_{m=n}^{\infty}\frac{1}{m^{2}}$?

In case the question didn't display in the title correctly: How do we bound the function $\frac{-1}{2}\sum_{m=n}^{\infty}\frac{1}{m^{2}}$? I think a way I can do this is to show that $$\sum_{m=n}^{\...
1
vote
2answers
54 views

Error in approximating e via a finite sum

I need some help with a homework problem. I have to find an upper bound for the error in approximating $e$ by the series $$\sum_{k=0}^{n} \frac{1}{k!}$$ I thought about using Taylor's theorem with ...
0
votes
4answers
82 views

Why does the definiton of the Euler's number not violate the rule agaisnt division by zero? [duplicate]

e= appears to be defined as the sum of the series 1/n! as n goes from zero to infinity. But this implies that the first term is 1/0! which appears to violate the rule against division by zero
0
votes
3answers
87 views

Is this : $\lim \sup\frac{\sigma(n)}{n} , n \to\infty $ has a finite limit?

The asymptotic growth rate of the sigma function can be expressed by : $$\lim \sup\frac{\sigma(n)}{n\log(\log(n))}=e^{\gamma}$$ $$n \to\infty$$ according to the above limit , Is this : $$\lim \sup\...
1
vote
1answer
44 views

What Does The Sequence $a_ N = \frac{\sum_{j=1}^{N} \{\frac{N}{j}\} }{N}$ Converge to?

In some of my number theoretical calculations I saw the sequence $$a_ N = \frac{\sum_{j=1}^{N} \{\frac{N}{j}\} }{N}$$ for $1\leq N$ and $\{x\}$ means the fractional part of $x$. I checked with a ...
1
vote
1answer
35 views

Find the region R for which the sequence converges

Find the region $(x,y) \in R$ for which the following sequence converges $$\left| e^n\frac{(\sqrt{y}-\sqrt{x})^{2n}}{x^n} \right| \to 0$$ I am currently doing number theory research on studying the ...
0
votes
1answer
209 views

Solve the differential equation using separation of variables: $\frac{dy}{dx} = e^{3x+2y}$

I need to solve using the method of separation of variables. I got to this point but I'm not sure if I'm on the right track: $$\frac{-1}{2e^{2y}} + C = \frac{e^{3x}}{3} + C$$ It looks like now I ...
0
votes
2answers
62 views

L'Hôpital's rule exercise with sqrt(x) as exponent

I'm a bit stuck trying to find the limit of the following function: $$\lim_{x \to 0^+}\,\,{x^{\sqrt{x}}} $$ We are expected to use L'Hôpital's rule, and thus far I've managed to resolve the equation ...
0
votes
1answer
29 views

Solving a variable in a matrix equation?

I am having trouble solving for a in the problem below. I've simplified it down to: $e^{14} = ln(e^e \cdot a)$. I'm not really sure where to go from here.
2
votes
2answers
65 views

How to solve the derivative of $b^x$ using the defintion

I know that the derivative of $b^x$ is just $b^x \log{(b)}$, and I've seen it being derived using chain rule and such (not that I understand how it's done, I just learned about $e$ today so using the ...
1
vote
1answer
653 views

How is de = 1 (mod ϕ(n)) calculated

I am reading RSA algorithm. So, I was writing a question but I saw this question and still couldn't understand it. If $$e\cdot d \equiv 1 \pmod{\varphi(n)},$$ then $$ed=k\cdot \varphi(n)+1, \qquad k\...
2
votes
3answers
183 views

Is it possible to intuitively explain, how the three irrational numbers $e$, $i$ and $\pi$ are related?

I read a bit about this equation: $e^{i\pi}=-1$ For someone knowing high school maths this perplexes me. How are these three irrational numbers so seemingly smoothly related to one another? Can this ...
5
votes
6answers
226 views

Graph of the function $x^y = y^x$, and $e$ (Euler's number).

Earlier, I was using the Desmos Graphing Calculator, and I wanted to remind myself of what the graph of the function $x^y = y^x$ looked like. If you have never seen what it looks like before, it is ...
0
votes
1answer
67 views

Justify the steps of the integral representations of the Euler-Mascheroni constant $\gamma$

These are the steps in order to get the Euler-Mascheroni constant $\gamma$ there were steps before where I'm starting but I didn't have questions about the justifications of those so I didn't include ...