Questions regarding the Taylor series expansion of univariate and multivariate functions, including coefficients and bounds on remainders. A special case is also known as the Maclaurin series.

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Develop the Taylor series of $\ln(z^2-5z+6)$ in $z=0$

Also, determine the radius of convergence. $\ln$ is the principal branch of the complex logarithm. What I've tried is splitting the function into $\ln(z-3)+\ln(z-2)$ and then finding the formula for ...
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2answers
68 views

How to find a Taylor series for $e^{x^2-1}$? [on hold]

How do I proceed to write a taylor series expansion for $e^{x^2-1}$? I know the series for $e^x$: it is $1+(x)+(x^2/2!)+\dots$ Edit: Would a Maclaurin series expansion be different?
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2answers
35 views

How to fastest approximate definite integrals

I know that a definite integral is a limit of Riemann sums. So if one wanted to estimate a definite integral (because one might not be able to find an antiderivative), then one can just take enough ...
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0answers
25 views

Compute radius of convergence and the first three coefficients of a function

Let $\displaystyle f(z) = \frac{z+1}{(2z+1)(1+ \sin z)}$, with serie expansion $\sum_{n=0} ^\infty a_n z^n$ around zero. Now I want to compute the radius of convergence and the first three ...
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25 views

Taylor expansion of the solutions of the equation $1-4 \cos(\frac{1}{x})+8x \sin(\frac{1}{x})=0$

In following article, I give an example of a function whose derivative at 0 is equal to 1 but which is not increasing near 0. The function is: $$\begin{array}{l|rcl} f : & \mathbb{R} & ...
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4answers
168 views

The even-numbered coefficients of the Maclaurin series of $ \frac{1}{\cos(x)} $ are odd integers.

Let’s consider $ G(z) \stackrel{\text{df}}{=} \dfrac{1}{\cos(z)} $ as the exponential generating function of the sequence of Euler numbers. How can one prove that in the Maclaurin series of $ G $, $$ ...
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1answer
12 views

Reasoning behind method of steepest descent

I am considering the method of steepest descent from my notes. I have written that $$\int_a^b dx e^{g(x)} \sim e^{g(x_0)} \int_{\infty}^{\infty}dx \exp \left[-\frac{1}{2}(x-x_0)^2|g^"(x_0)|\right] ...
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1answer
19 views

Two variables Taylor's expansion

I guess that Taylor's expansion about $(0,0)$ is useful for finding value of $\dfrac{\partial^{4n}}{\partial x^{2n}\partial y^{2n}} \left (\dfrac{1}{1+x^2+y^2}\right)(0,0) $. How can it do?
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35 views

Taylor Series confusion [on hold]

Can someone explain how to do this problem? I just started Taylor series and I am super confused on how to do it.
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1answer
20 views

Estimate $\ln\left( 1.04^{0.25} + 0.98^{0.2} -1 \right)$ with 2D Taylor

I need to estimate $\ln\left( 1.04^{0.25} + 0.98^{0.2} -1 \right)$ with a Taylor approximation of a two variable function (i.e. x and y). Eventually I managed to pull the (presumably) correct ...
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2answers
35 views

Find $\lim\limits_{x \to 0} \frac{(1+3x)^{1/3}-\sin(x)-1}{1-\cos(x)}$

I would like to find using Taylor series : $$\lim\limits_{x \to 0} \frac{(1+3x)^{1/3}-\sin(x)-1}{1-\cos(x)}$$ So I compute the taylor series of the terms at the order $1$ : $(1+3x)^{1/3}=1+x+o(x)$ ...
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0answers
23 views

Radius of convergence of $x/sinh(x)$

the function $\mathbb{R}\ni x\mapsto \frac{x}{\sinh(x)}\in\mathbb{R}$ can be written in a neighborhood of $0\in\mathbb{R}$ as a Taylor series, i.e. $\frac{x}{\sinh(x)}=\sum\limits_{k=0}^{\infty} a_k ...
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1answer
31 views

how to understand Taylor's inequality intuitively?

I am learning the Taylor Series at the moment and I am trying to figure out how to understand Taylor's inequality intuitively. I know you can integrate repeatedly and prove the inequality is ...
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3answers
23 views

Power series expansion using Taylors Theorem.

So the function $f(x)=3x^2-6x+5$ needs to be written as a power series expansion around $x=a$ and the goal is to show $x=a$ is $f(x)$ for every $a$. So I started off by finding up to the third ...
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1answer
29 views

Are the coefficients of a Taylor series bounded when the function is?

Say that I have three real functions $f(x)$, $g(x)$, and $h(x)$ such that $f(x)\le g(x)\le h(x)$ for all real $x$. Additionally, $f(x)$ and $h(x)$ are logarithmically convex. Can I make any definite ...
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1answer
28 views

Maclaurin Series - finding the co-efficients for functions that require the product rule

I have just been introduced to the Maclaurin series, and one of the questions I have requires that I find the Maclaurin series for the function $$ f(x) = 3x^2\sin(2x)$$ The way I considered ...
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2answers
54 views

Taylor expansion of $\sin(x)$ and periodicity

Consider that $$\sin x=\sum_{n=0}^\infty(-1)^n\frac{x^{2n+1}}{(2n+1)!}$$ and $$(a+b)^k = \sum_{i=0}^k {k \choose i}a^ib^{k-i}.$$ Then: $$\sin (x + ...
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1answer
12 views

Approximation of monthly payment using Taylor expansion

I am trying to understand what does APR(annual percentage rate) and how it is calculated. Thanks to Wikipedia, I got the formula of monthly payment for a fixed rate multi-year mortgage in the ...
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1answer
50 views

Taylor polynomial for an integral

This is the first time encountering a Taylor expansion along with an integral, so I am wondering how I should proceed. Question: $Consider \space the \space function$ $$F(x) = ...
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1answer
20 views

Taylor series expansion approximating an integral?

I need to use the Taylor series expansion of $$\frac{1}{1+3x^2} $$ to find a series approximating $$\int_0^1 \frac{1}{1+3x^2} \, dx $$ and $$\int_0^{1/3} \frac{1}{1+3x^2} \, dx $$ I tried to start the ...
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26 views

Series Expansion from Polynomial w/ Coefficients [closed]

I have four coefficients to a 4-the order polynomial. Besides having some stroke of luck finding a pattern (that would be difficult considering the coefficient values) what is the best way to approach ...
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3answers
50 views

Determine the Taylor expansion for the solution of the differential equation

I'm given the following: $$\begin{cases}\frac{dx}{dt} = t^2x\\ x(0) = 1\end{cases}$$ I'm asked to determine the taylor expansion for the solution to the $t^{10}$ term. $$x(t) = a_0 + a_1 t + a_2 ...
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1answer
22 views

Taylor Series Expansion for ${z^2+4z^4+z^6}/(1-z^2)^3$

So I know for sure that the Taylor Series expansion for $1/(1-z^2)^3$ is $\sum {k(k-1)z^{2k-4}/{2}} $ assuming |x|<1. But what do we do with the top? I think its already in the expanded form, ...
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23 views

Find out if $f''(0)$ exist and $x=0$ is a inflection point

Let $f(x)=\begin{cases} \displaystyle\sin(\frac{1}{x})\cdot e^{\frac{-1}{x^2}} &\text{for } x \neq 0\\0 &\text{dla } x=0 \end{cases}$ Find out if $f''(0)$ exist and $x=0$ is a inflection ...
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1answer
32 views

Find the radius of convergence of the Maclaurin series $x\cdot ln\left(x^2+\sqrt{x^4+9}\right)$

First you need to expand the function in a Maclaurin series. Then find the radius of convergence of the Maclaurin series. My question: $$x\cdot ln\left(x^2+\sqrt{x^4+9}\right)$$ My solution: ...
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1answer
13 views

Remainder Taylor series two+ variables

Hard to find an article / tutorial specifically about this subject online.... Can anyone explain / send link to explanation or tutorial regarding how to calculate remainder for multi-variable taylor ...
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1answer
24 views

Show that $\sum r^n cos(nx)=rcos(x)-r^2/(1-2rcos(x)+r^2)$

I'm a little unsure about how to approach this. I've been told that we have to use the relationship that $\sum r^n=1/1-r$. However, I'm not too sure what to do with the $\cos(nx)$. Can someone give ...
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1answer
22 views

Taylor Series expansion and radius of convergence for $e^z+e^{-z}+2cosz/4$

So I did this by taking apart bits of that long equation: $e^z=\sum z^n/n!$, $e^{-z}=\sum(-z)^n/n!$ $2\cos z=e^{iz}+e^{-iz}$ So when we put these together as a Taylor Series, do we just add them ...
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170 views

Global and local maxima in a weighted sum of logarithms of linear functionals?

Is is possible to describe, and locate efficiently, the maxima of the function below in the parameters $\mathbf{x}$ $$\sum_{i} p_i \log( N + \sum_j x_j[B_j +(A_j-B_j)\delta_{ij} + min(A_j,B_j) ]) ...
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19 views

multivariable linearization

I have been asked to linearise the fallowing equilibrium points are phy=theta yaw=0 x,y,z=0 The idea I have using V'z as a model: -g+(kcm/m)(cos(phy)cos(thata)*voltages + ...
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22 views

How expand an equation in powers of two variables?

Let $$ \varphi=\int\frac{dr}{r^2\sqrt{\frac{1}{b^{2}}-\left(1-\frac{s}{r}\right)\frac{1}{r^{2}}}} $$ Is it possible to expand the above equation in powers of $\frac{s}{r}$?. I know that after ...
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1answer
70 views

Find the value of Taylor coefficient $a_5$ for the function $ \int_0^x (e^{-t^2}+\cos t) \, dt$

Find the value for $a_5$ If $ \int_0^x (e^{-t^2}+\cos t) \, dt$ has the power series expansion $\sum_1^\infty a_nx^n$, then find $a_5$ up to three correct decimal places. I think it is a Taylor ...
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1answer
32 views

Maclaurin Series: Complex Analysis

Question: Use the representation $\sin z = \sum\limits_{n=0}^\infty (-1)^n\frac{z^{2n+1}}{(2n+1)!}$, $|z|<\infty$ to write the Maclaurin series for the function $f(z) = \sin z^2$ and point out how ...
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443 views

This one weird thing that bugs me about summation and the like

Most of us know $$\sum_{n=a}^b c_n=c_a+c_{a+1}...+c_{b-1}+c_b$$ Some of us know $$\prod_{n=a}^b c_n=c_a \cdot c_{a+1}...c_{b-1} \cdot c_{b}$$ A few of us know ...
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0answers
20 views

Taylor expansion of a power function

I was wondering about Taylor expansions of functions of the form $x^p$, where p is a real number, about $x = 0$. It seems clear how to do it about any other point, but what happens to the series as I ...
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1answer
61 views

What are Bernoulli numbers?

In my calculus class, my teacher said that if one was to try to calculate the maclaurin or taylor series of $\tan x$ by strictly using the definition , then you would run into many problems and your ...
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3answers
60 views

Calculate $\sqrt{5}$ using taylor series to the accuracy of 3 digit after the point $(0.5*10^{-3})$.

I need to calculate $\sqrt{5}$ using taylor series to the accuracy of 3 digit after the point $(0.5*10^{-3})$. I defined : $$f(x)=\sqrt{x}$$ Therefore : $$f'(x)=\frac{1}{2\sqrt{x}}$$ ...
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1answer
25 views

At what points is the function $f(z) = \frac{1}{2+e^z}$ holomorphic?

I need to determine at which points this function is holomorphic. I attempted to use the Cauchy-Riemann equations, but that got too messy and so I'm trying to find another route. In the first part of ...
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3answers
52 views

find taylor series to fourth term

I'm wondering if there is faster method than just calculating derivatives with finding taylor series up to 4 term of function $\displaystyle f(x)=\frac{(1+x^4)}{(1+2x)^3(1-2x)^2}$
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85 views

How to find the Maclaurin series for $e^{-x^2}$

I don't know how to get $$1-x^2+\frac{x^4}{2!}-\cdots.$$ I think it is too complex, if not impossible, to just use the definition of Maclaurin series. Using the definition: consider the situation ...
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1answer
31 views

How do you prove that $\int_{1}^{n}\ln x \,dx \geq \sum_{i = 1}^{n}\ln i -\frac{\ln n }{2}$?

In Upfal's probability textbook Lemma 5.8, he tries to justify $\int_{1}^{n}\ln x \,dx \geq \sum_{i = 1}^{n} \ln i -\frac{\ln n }{2}$ with concavity of $\ln x$, I don't quite follow his argument, can ...
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1answer
66 views

How can I solve the integral in the error function $\mbox{erf}(x)$?

To get from this To this series I can't seem find the step-by-step solution anywhere.
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17 views

Multivariate Taylor Series

If $u(x,t)=\alpha + u_1(t)\xi(x,t)+\frac{1}{2}u_2(t)[\xi(x,t)]^2+...$ for small $\xi<0$ apparently $c(u)=c(\alpha)+\xi u_1(t)c'(\alpha)+ O(\xi^2)$ I assume their is some sort of taylor expansion ...
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1answer
61 views

Solve limit of integral through taylor

Show using Taylor expansion that $$\lim_{r\to 0} \frac4{\pi r^2} \int_0^{2\pi} f(a+r\cos \theta , b +r\sin \theta)\cos{2\theta}d\theta = f_{xx} (a,b) - f_{yy}(a,b)$$ where $f:\mathbb R^2 \to ...
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1answer
47 views

Find the Taylor Series expansion of the given analytic function

Find the Taylor Series expansion of the given analytic function $f(z)$, centered at point $z_0$; find the disk of convergence. a) $f(z)=\frac{1}{-2+3i-z}$ $z_0=3$ b) $f(z)=(2-z)\cos{(3z^2)}$ ...
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1answer
34 views

Find the Taylor series expansion (centered at $z_{0}=0$) of the function $f(z)=\sin(z^3)$.

Find the Taylor series expansion (centered at $z_{0}=0$) of the function $f(z)=\sin(z^3)$. Use this expansion: a) to find $f^{69}(0)$; b) to compute the integral transversed once in the positive ...
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2answers
27 views

Expand the function in a Maclaurin series $\ln(5\cos^{3}(x))$

$$\ln(5\cos^{3}(x))$$ Need to be expanded: $x^{4}$ I need to end this problem. So I laid the beginning of the function. $$\cos x=1-\frac{x^2}{2!}-\frac{x^4}{4!}+o(x^4)$$ ...
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1answer
25 views

Taylor/ Maclaurin Series: Solving for x

Hi guys I was wondering how to do this question. I'm not sure what method to use.
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2answers
20 views

taylor series for two variables

The theorem I have been given for this is $$f(x,y)=f(a+u,b+v)=f(a,b)+\sum \limits_{k=1}^{\infty} \frac1{k!} \bigg(u\frac{\partial}{\partial x}+v\frac{\partial}{\partial y}\bigg)^kf(a,b)$$ where ...
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0answers
27 views

Showing a hyperbola in polar form approaches two asymptotes

Consider a curve given in polar coordinates by $r(θ)=\frac{1}{1+e\cos\theta}$, where $e≥0$. When $e>1$, show that the curve approaches two asymptotes, find them and sketch the curve. Hint: If the ...