Series Definition and 998 Threads

  1. Rfael69

    I Is there an alternative to Taylor series but with differences?

    is there an equivalent to taylor series but with differences instead of derivatives ? are Newton series analogue to Taylor series ?
  2. J

    Calculating the sum of a series of cubes

    Mentor note: Moved from technical math section, so missing the homework template filling in the boxes is easy, 1,3,6,10,15 second is just squares of that, 1,9,36,100,225 But how I anyone supposed to find and expression for this? This is from a textbook on elementary algebra, the specific...
  3. Ineedhelpwithphysics

    Finding parallel or in-series resistors

    I cannot understand why the 45 ohm resistor is parallel to the 15 ohm resistor. It's been defined that if two or more resistors are in parallel they same common connection points. I don't see these connections points. Is the junction point after the ammeter signifying that the 45 ohm and 15 ohm...
  4. E

    I Fundamental theorem of arithmetic from Jordan-Hölder theorem

    I was intrigued by a comment in Brilliant.org: Besides the proof provided by Brilliant, I also found a couple of other websites. But none of these proofs were entirely clear to me. So I tried to come up with my own proof. Since I am not a group theorist, I wanted to ask if the proof makes...
  5. H

    Math terminology in my Taylor Series expansion?

    I have another dilemma with terminology that is puzzling and would appreciate some advice. Consider the following truncated Taylor Series: $$\begin{equation*} f(\vec{z}_{k+1}) \approx f(\vec{z}_k) + \frac{\partial f(\vec{z}_k)}{\partial x} \Delta x + \frac{\partial f(\vec{z}_k)}{\partial...
  6. Heisenberg7

    Telescopic Series (Trigonometry)

    Greetings, I would like to gain some insight when it comes to dealing with this problem. Personally, I wasn't able to solve it. I had to look for the solution in the book. I can just tell you that it's a telescopic series, the rest would be too much. You don't have to post the whole solution...
  7. A

    I Method for finding a complex series?

    We are working with series currently, and some of the problems ask you to create a general term and write it in series summation form. Some of it is a no-brainer, but other ones, I'm at a loss as to how they expect us to get the answer without a ton of trial and error. For example, there is...
  8. A

    Maclaurin Series When 0 is in the Denominator?

    I have tried a few things and can't figure this out. If I separate the top and bottom, the top obviously quickly goes to 0, so there's no series after 1 derivative (f'(2x) = 2, then f''(2x) = 0), so I can't separate them and do anything with it And if I do it with ## 2x(e^{2x}-1)^{-1} ##...
  9. L

    Taylor Series Expansion Confusion

    For context, this is when deriving the Boltzmann distribution by using a canonical ensemble (thermodynamics). omega is a function to represent number of microstates. According to wikipedia... is the first order expansion around 0 (Maclaurin series). My confusion: What are even...
  10. A

    Infinite Series (Geometric) Problem

    As far as how far I've gotten, I split the non-repeating portion of the series apart from the repeating portion, set r as ## 10^{-6} ## and get this: ## 0.65+285714/9999990 ## From here though, I don't see how to simplify that fraction without something extremely tedious, like pulling out...
  11. T

    I Evaluating Taylor Series at the Mid-Point

    Hi all, I came across the following stackexchange post and was wondering if anyone could give any elaboration for why the answer claims that evaluating the Taylor Series resulted in ##\mathcal{O}(\epsilon^{3})## errors? I have not encountered such an expansion before. EDIT: The equation at hand...
  12. M

    Proving convergence and divergence of series

    For this problem, Let ##a_n = \frac{1}{n(\ln n)^p}## ##b_n = \frac{1}{(n \ln n)^p} = \frac{1}{(n^*)^p}## We know that ##\sum_{2 \ln 2}^{\infty} \frac{1}{(n^*)^p}## is a p-series with ##n^* = n\ln n##, ##n^* \in \mathbf{R}## Assume p-series stilll has the same property when ##n^* \in...
  13. askingask

    Peltier cell in series both electrically and thermally

    So here you can see the basics behind a thermocouple. What people usually do, is that they connect these junctions electrically in series and thermally in parallel. Now another thing people do is cascading several peltier modules. Now my thought was, why not connect them electrically...
  14. MatinSAR

    Calculating Laurent series of complex functions

    1. ##f(z)=\dfrac {\sin z}{z- \pi}## at ##z=\pi## : $$ \dfrac {\sin z}{z- \pi}=\dfrac {\sin(\pi +z- \pi)}{z- \pi}=\dfrac {- \sin(z- \pi)}{z- \pi}=\dfrac {-1}{z- \pi} \sum_{n=0}^\infty \dfrac {(-1)^n (z- \pi)^{2n}}{(2n+1)!}$$My answer has extra ##\dfrac {-1}{z- \pi} ## according to a calculator...
  15. C

    Valid conclusion for an absolutely convergent sequence

    Hello, this is my attempt for #19 for 11.6 of Stewart's “Multivariable Calculus”. The question is to determine whether the series is absolutely convergent, conditionally convergent, or divergent. The answer solutions used a ratio test to reach the same conclusion but I used the comparison test...
  16. Euge

    POTW Sum of an Alternating Series

    Find, with proof, the sum of the alternating series $$\sum_{n = 0}^\infty \frac{(-1)^n}{(2n+1)^3}$$
  17. chwala

    Use method of difference to find sum of series

    My interest is on the (highlighted part in yellow ) of finding the partial fractions- Phew took me time to figure out this out :cool: My approach on the highlighted part; i let ##(kr+1) =x ## then, ##\dfrac{1}{(kr+1)(kr-k+1)} = \dfrac{1}{x(x-k)}## then...
  18. P

    I Question on an infinite summation series

    Is the infinite series ##\sum_{n=1,3,5,...}^\infty \frac {1} {n^6}## somewhat related to the Riemann zeta function?The attached image suggest the value to be inverse of the co-efficient of the series.Is there any integral representation of the series from where the series can be evaluated?
  19. G

    Second order differential - Tanks in series cooling coil

    I'm stuck on a problem: T1 = dT2/dt + xT2 - y T2 = (Ae^(-4.26t))+(Be^(-1.82t))+39.9 I'm unsure how to proceed
  20. T

    B Are All Imaginable Integer Series Necessarily Infinite?

    Any set of a series of numbers consisting of increasing integer members, all of which are determined by a common proposition or characteristic, will always be infinite in size. Examples… Prime numbers Mersenne primes Odd perfect numbers(if they exist) Zeroes of the Zeta function Regardless...
  21. S

    Why Do Capacitors Behave Differently in Series and Parallel Configurations?

    Consider the above diagram. Once the first capacitor is charged, clearly it will have a voltage ##E##. Then when the switch is flipped, the cell no longer matters (there is no complete circuit which goes through the cell), so we have the first capacitor connected to the second one, and it looks...
  22. RChristenk

    Logarithmic Series question for finding ##\log_e2##

    By definition: ##\log_e(1+x)=x-\dfrac{x^2}{2}+\dfrac{x^3}{3}- \cdots ## ##(1)## Replacing ##x## by ##−x##, we have: ##\log_e(1-x)=-x-\dfrac{x^2}{2}-\dfrac{x^3}{3}- \cdots## By subtraction, ##\log_e(\dfrac{1+x}{1-x})=2(x+\dfrac{x^3}{3}+\dfrac{x^5}{5}+ \cdots)## Put ##...
  23. P

    On pointwise convergence of Fourier series

    So, the function is piecewise continuous (and differentiable), with (generalized) one-sided derivatives existing at the points of discontinuity. Hence I conclude from the theorem that the series converges pointwise for all ##t## to the function ##f##. I've double checked with WolframAlpha that...
  24. P

    I How does the ratio test fail and the root test succeed here?

    The series that is given is $$\frac12+\frac13+\left(\frac12\right)^2+\left(\frac13\right)^2+\left(\frac12\right)^3+\left(\frac13\right)^3+\ldots.$$ Now, it's easy to see these are two separate geometric series, however, Spivak claims the ratio test fails because the ratio of successive terms...
  25. L

    Checking series for convergence

    Hi, I am having problems with task d) I now wanted to check the convergence using the quotient test, so ## \lim_{n\to\infty} |\frac{a_{n+1}}{a_n}| < 1## I have now proceeded as follows: ##\frac{a_{n+1}}{a_n}=\frac{\Bigl( 1 + \frac{1}{k+1} \Bigr)^{(k+1)^2}}{3^{k+1}} \cdot...
  26. justin___

    Finding an open-cicuit voltage, why is resistor in series ignored?

    I found how to get the solution to this question (the answer is 200V), but I don't understand why we ignore the 30kOhm resistor when using analysing the circuit. Because it is in series with the open voltage, wouldn't there be some voltage drop across the resistor that would affect the...
  27. Euge

    POTW A Series Converging to a Lipschitz Function

    Prove that the series $$\sum_{k = 1}^\infty \frac{(-1)^{k-1}}{|x| + k}$$ converges for all ##x\in \mathbb{R}## to a Lipschitz function on ##\mathbb{R}##.
  28. F

    Springs connected to a mass in series?

    I found the answer for the springs in parallel, but not for the ones in series. I believe I don't understand how the forces are interacting properly. Here's a force diagram I drew. Everytime I try to make equations from this though my answer dosen't make sense. The mass m has a gravititoanl...
  29. Euge

    POTW Does the Taylor series for arctan converge at x = 1?

    Show that $$\frac{\pi}{4} = 1 - \frac{1}{3} + \frac{1}{5} - \frac{1}{7} + \cdots$$
  30. Al-Layth

    Book recommendation for techniques of evaluating Series?

    TL;DR Summary: I am looking for a good thorough book that is devoted to assembling and explaining techniques of evaluating series. evaluating series is a very big problem for me right now. I know nowhere near as much about it as I do integration, and the main reason for this is that its quite...
  31. carlsondesign

    I What is the official name for a Field Series in mathematics/physics?

    I've been working on developing infinitesimal recursion (what I call continuous hierarchy), but I ended up arriving at "field series" instead. My searches didn't seem to come up with anything reasonable (battlefield the video game series), so I'm wondering what the official name for a field...
  32. PhysicsRock

    Why Capacitors in Parallels vs. Series: Coaxial Capacitor Case

    So my idea was to separate the capacitor into two individual ones, one of length ##l - a## filled with a vacuum and one of length ##a## filled with the glass tube. The capacitances then are $$ C_0 = \frac{2 \pi \varepsilon_0 (l-a)}{\displaystyle \ln\left( \frac{r_2}{r_1} \right)} $$ for the...
  33. J

    A Margules' Power Series Formula: Deriving Coefficients

    Margules suggested a power series formula for expressing the activity composition variation of a binary system. lnγ1=α1x2+(1/2)α2x2^2+(1/3)α3x2^3+... lnγ2=β1x1+(1/2)β2x1^2+(1/3)β3x1^3+... Applying the Gibbs-Duhem equation with ignoring coefficients αi's and βi's higher than i=3, we can obtain...
  34. Euge

    POTW A Test for Absolute Convergence of a Series

    Let ##\{a_n\}_{n = 1}^\infty## be a sequence of real numbers such that for some real number ##p > 1##, ##\frac{a_n}{a_{n+1}} = 1 + \frac{p}{n} + b_n## where ##\sum b_n## converges absolutely. Show that ##\sum a_n## also converges absolutely.
  35. Euge

    POTW Fourier Series on the Unit Interval

    Evaluate the Fourier series $$\frac{1}{\pi^2}\sum_{k = 1}^\infty \frac{\cos 2\pi kx}{k^2}$$ for ##0 \le x \le 1##.
  36. S

    I Geometry of series terms of the Riemann Zeta Function

    This is an Argand diagram showing the first 40,000 terms of the series form of the Riemann Zeta function, for the argument ##\sigma + i t = 1/2 + 62854.13 \thinspace i## The blue lines are the first 100 (or so) terms, and the rest of the terms are in red. The plot shows a kind of approximate...
  37. S

    Need help with a (apparently) difficult series

    This is the series: $$\sum_{n=1}^{+\infty}\sin(n)\sin\left(\frac{1}{n}\right)\left(\cos\left(\frac{1}{\sqrt{n}}\right)-1\right)$$
  38. F

    Looking for a particular function

    TL;DR Summary: I want to find a function with f'>0, f''<0 and takes the values 2, 2^2, 2^3, 2^4,..., 2^n Hello everyone. A professor explained the St. Petersburgh paradox in class and the concept of utility function U used to explain why someone won't play a betting game with an infinite...
  39. M

    A Infinite series of this type converges?

    ##\sum_{n=1}^\infty n^{-a}## converge s for ##a\gt 1## - otherwise diverges. Is there any theory for ##a_n##? For example ##a_n\gt 1## and ##\lim_{n\to \infty} a_n =1##. How about non-convergent with ##\liminf a_n=1##?
  40. A

    A Completeness of the formal power series and valued fields

    I had difficulty showing this no matter what I tried in (a) I am not getting it. Here for p(t) in K[[t]] : ## |p|=e^{-v(p)} ## where v(p) is the minimal index with a non-zero coiefficient. I said that p_i is a cauchy sequence so, for every epsilon>0 there exists a natural N such that for all...
  41. L

    I Taylor Expansion Question about this Series

    Can you please explain this series f(x+\alpha)=\sum^{\infty}_{n=0}\frac{\alpha^n}{n!}\frac{d^nf}{dx^n} I am confused. Around which point is this Taylor series?
  42. chwala

    Solving the Fourier cosine series

    My question is; is showing the highlighted step necessary? given the fact that ##\sin (nπ)=0##? My question is in general i.e when solving such questions do i have to bother with showing the highlighted part... secondly, Can i have ##f(x)## in place of ##x^2##? Generally, on problems to do...
  43. chwala

    Solve the problem involving sum of a series

    Attempt; ##\dfrac{1}{r(r+1)(r+2)} -\dfrac{1}{(r+1)(r+2)(r+3)}=\dfrac{(r+3)-1(r)}{r(r+1)(r+2)(r+3)}=\dfrac{3}{r(r+1)(r+2)(r+3)}## Let ##f(r)=\dfrac{1}{r(r+1)(r+2)}## ##f(r+1)= \dfrac{1}{(r+1)(r+2)(r+3)}## Therefore ##\dfrac{3}{r(r+1)(r+2)(r+3)}## is of the form ##f(r)-f(r+1)## When...
  44. chwala

    Solve the problem involving sum of a series

    My attempt; ##r^2+r-r^2+r=2r## Let ##f(r)=(r-1)r## then it follows that ##f(r+1)=r(r+1)## so that ##2r## is of the form ##f(r+1)-f(r)##. When ##r=1;## ##[2×1]=2-0## ##r=2;## ##[2×2]=6-2## ##r=3;## ##[2×3]=12-6## ##r=4;## ##[2×4]=20-12## ... ##r=n-1##, We shall have...
  45. S

    Switching between parallel and series connections (solar)

    We're off grid at 57degrees north. Our source of electricity is solar panels, with a diesel generator as backup. The solar has served us well, until this November, where we had almost 8 weeks of 0 sunshine. I got sick of running the generator. It's noisy, it needs refueling, smells... So I...
  46. supak111

    Calculate current in a 120 VAC circuit with a series 10uF capacitor

    Hi can someone tell me please how much current is passed though below circuit: 120 AC 60Hz mains power going through a 10uF 500v capacitor in series
  47. tworitdash

    A How to sum an infinite convergent series that has a term from the end

    From my physical problem, I ended up having a sum that looks like the following. S_N(\omega) = \sum_{q = 1}^{N-1} \left(1 - \frac{q}{N}\right) \exp{\left(-\frac{q^2\sigma^2}{2}\right)} \cos{\left(\left(\mu - \omega\right)q\right)} I want to know what is the sum when N \to \infty. Here...
  48. H

    For what values of ##\beta## does the series converge?

    For what values of β the following series converges $$ \sum_{k=1}^{\infty} k^{\beta} \left( \frac{1}{\sqrt k} - \frac{1}{\sqrt {k+1}}\right) $$ I thought of doing it like this $$ \frac{k^{\beta} }{\sqrt k} - \frac{k^{\beta} }{\sqrt{k+1}}$$ $$0 \lt \frac{k^{\beta} }{\sqrt k} - \frac{k^{\beta}...
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