Sequence Definition and 1000 Threads

  1. alexmahone

    MHB Prove that there is a strictly decreasing sequence

    Given any irrational number c > 0, prove that there is a strictly decreasing sequence of rational numbers that converges to c.
  2. T

    Proving Limit of x^(1/n) is 1 for x>0

    Homework Statement Rigorously show that for all x>0, the limit of {x^{1/n}} is 1. Homework Equations The Attempt at a Solution |x^{1/n}-1|\leq\epsilon I'm not sure where to go from here...just looking for a little guidance.
  3. A

    Sequence that has all rational numbers

    Homework Statement Construct a sequence that has all rational numbers in it Homework Equations None. The Attempt at a Solution Here are my thoughts, though I have no solutions yet. If I construct a sequence Sn= n*sin(n)-1/n, will it work? Thanks guys!
  4. L

    Show Convergence of sequence (1 + c)(1 + c^2) (1 + c^n)

    Homework Statement Hey, so here is the problem: Suppose 0≤c<1 and let an = (1 + c)(1 + c2)...(1 + cn) for integer n≥1. Show that this sequence is convergent. Well I understand the basic concepts of proving convergence of sequences, but in class we've only ever done it with sequences where...
  5. C

    Is the Sequence Defined by x_n+1 = x_n/2 + 1 Bounded Above by 2?

    Homework Statement Show that the sequence (x_1,x_2,x_3,...) defined by; Let x_1=1 for each n \in \mathbb{N} x_{n+1}= \frac{x_n}{2}+1 x_2=\frac{3}{2} Show that this sequence is bounded above by 2; that is prove that x_n\leq2 for all n\in\mathbb{N} The Attempt at a...
  6. L

    Calculating a limit of a sequence

    Hi guys, Homework Statement I'm trying to calculate the limit of the following sequence: an:= (\frac{n^{2}+10}{n^{2}-5n})^{(3n^{2}+2)} 2. The attempt at a solution Ok so I got this so far: an =...
  7. G

    A metric space of equivalent sequence classes

    A metric space of equivalent Cauchy sequence classes (Z, rho) is defined using a metric of the sequence elements in the space (X,d), where d is from XX to R (real numbers). The metric of the sequence classes is rho = lim d(S, T), where S and T are the elements of the respective sequences. To...
  8. Y

    Hoffman coding in 8bit sequence

    A data file contains a sequence of 8-bit characters such that all 256 characters are about as common: the maximum character frequency is less than twice the minimum character frequency. Prove that Huffman coding in this case is not more efficient than using an ordinary 8-bit fixed-length code...
  9. A

    Subsequence of a cauchy sequence in R

    Homework Statement If \{a_{n}\}\in\mathbb{R} is Cauchy, \forall\epsilon>0,\exists a subsequence \{a_{k_{j}}\} so that |a_{k_{j}}-a_{k_{j+1}}|<\frac{\epsilon}{2^{j+1}}. The Attempt at a Solution Since \{a_{k_{j}}\} is Cauchy,\forall\epsilon>0,\exists N_{\epsilon} such that for j,j+1\geq...
  10. H

    Proving the Limit of a Sequence Math Problem with Continuous Function f(x)

    Homework Statement Prove that if f(x) is continuous for 0<f(x)<1, then lim_{n->\infty}\frac{1}{n}[(n+1)(n+2)(n+3)...(2n)]^{\frac{1}{n}}=\frac{4}{e}. Homework Equationsf(x)=log(1+x) The Attempt at a Solution We know that...
  11. M

    Show Arithmetic Sequence: V0=4, Vn+1=√Vn2+2n+3

    Homework Statement V0=4 V_{n+1}=\sqrt{V_{n}^{2}+2n+3} Homework Equations Show that Un is an arithmetic sequence. The Attempt at a Solution I counted Vn and i found that it equals: V_{n}=\sqrt{(Vn+2)^{2}+2} what is there to do after this?
  12. F

    Summing a Sequence: Finite or Infinite?

    I've created two summations for my coursework, now I need to show whether or not the summations are finite or infinite. The 2 summations are very similar: With the n/2 removed it was easy enough to show the sum was equal to 1 [edit: I now realize I may have this wrong], now with the n/2 term...
  13. I

    Syntax for a sequence in a set X

    Syntax for a sequence "in" a set X It is well-known shorthand to say that a sequence of real numbers x_n is a sequence "in R". (Of course we do not mean that the function x_n is an element of R). In such a case, is it permissible to replace the word "in" by the element symbol, or is this not...
  14. V

    Product of a specific sequence of prime number squares

    Here is a good question for maths enthusiasts. I really find this sum very tough. Any help, advice or guidance for this question will be greatly appreciated. find the product upto n terms (1+(1/2^2)) . (1+(1/3^2)) . (1+(1/5^2)) . (1+(1/7^2)) . (1+(1/11^2))...upto n terms Where the nth...
  15. S

    I have that the sequence [itex]a_n=\{2-(-1)^n\}[/itex] not converges.

    I have that the sequence a_n=\{2-(-1)^n\} not converges. I must show this with the rigorous definition. I think use \exists{\epsilon>0}\forall{N\in\mathbb{N}}\exists{n\geq N}:|a_n-\ell|\geq\epsilon How i can continue?
  16. M

    Convergence and Continuity of Cauchy Sequences with Fixed Points

    Let f : [a,b] → [a,b] satisfy |f(x)-f(y)| ≤ λ|x-y| where 0<λ<1. Prove f is continuous. Choose any Xo ε [a,b] and for n ≥ 1 define X_n+1 = f(Xn). Prove that the sequence (Xn) is convergent and that its limit L is a 'fixed point' of f, namely f(L)=L
  17. M

    Prove cauchy sequence and thus convergence

    Let (Xn) be a sequence satisfying |Xn+1-Xn| ≤ λ^n r Where r>0 and λ lies between (0,1). Prove that (Xn) is a Cauchy sequence and so is convergent.
  18. A

    Sequence that converges to a point

    1.Problem Statement: If O is an open subset of ℝ does there exist a sequence in O that converges to x? Explain. 2.Relevant equations 3. The Attempt at a Solution So if I define a open subset of ℝ to be open if for all points x \in O there exists a ε-neighborhood _{V}ε (a)...
  19. T

    Where does this sequence converge?

    Homework Statement Does the sequence 1 + .4 + .16 +.064 Converge and where if so? So I started this problem out by making the a series equation Ʃ.4^n Where n=0 So since i believe this is the series equation for this sequence I now know that it does in fact converge because -1 < .4 ≤...
  20. M

    Writing a sequence in terms of n.

    Homework Statement given: Vn+1=Vn*cos(pi/2^(n+2)) Homework Equations Write a sequence Vn in terms of n The Attempt at a Solution we substitute n with n-1 and we get: V(n-1)+1= Vn-1*cos(pi/2^(n-1+2)) Vn=Vn-1*cos(pi/2^(n+1) Is this correct?
  21. D

    What is the sum of cubes in a series up to 'n' terms?

    Homework Statement find the sum of the series to 'n' terms (1^3 / 1 ) + (1^3 + 2^3 / 1+2 ) + (1^3 + 2^3 + 3^3 / 1+2+3 ) +... Homework Equations sigma n^2 = n(n+1)(2n+1) / 6 sigma n = n(n+1) / 2 The Attempt at a Solution numerator = 1^3 + 2^3 + ... n^3 denominator = 1+2+3+...n...
  22. M

    Is it possible to this sequence?

    Homework Statement given: Vn+1=Vn*cos(pi/2^(n+2)) and Vn= pi/2 Homework Equations Write Vn in terms of nThe Attempt at a Solution how can i start this. I already know that -1<cosx<1 and I've already proved that this sequence is a negative sequence. Then our teacher said if its...
  23. R

    Show this sequence converges and find its limit

    Homework Statement Suppose f is continuously differentiable, and a < b. The sequence is defined as follows: a_{n} = n\int_a^b \! f(x) \, \mathrm{d} x - n(\frac{b-a}{n})\displaystyle\sum\limits_{i=1}^n f(a + \frac{b-a}{n}i) The Attempt at a Solution I've been busting my *** with this one...
  24. I

    Math Proof: Uncountable binary sequence and a bijection from R to R-{0}

    Homework Statement Question 1: Prove that the cardinality of R (the set of all real numbers)is the same as the cardinality of R-{0} by constructing a bijective function from R to R-{0} Question 2: Let A be the infinite sequence of binary numbers as follows: A={(a1,a2,a3...)|ai= 0or 1 for...
  25. F

    Certain and Curious Number Sequence

    Certain and Curious Number Sequence (w/ primes) This is the number sequence a(x) whose output is determined by the greatest integer divisor n of any factorization of a with the additional rule that if an element is repeated in the factorization, the factorization must be thrown out. EX: a(56)...
  26. R

    Using the Sequence Criterion for Closedness

    For a subset C is a subset of R^d the following conditions are equivalent: (i) C is closed. (ii) For every sequence (x_n) is a subset of C which converges in R^d, the limit lim (as n goes to infinity) x_n = x must also lie in C. Using the above theorem for the Sequence Criterion for...
  27. T

    Convergence of a sequence in a metric space

    Homework Statement For x,y \in\mathbb{R} define a metric on \mathbb{R} by d_2(x,y) = |\tan^{-1}(x) - \tan^{-1}(y) | where \tan^{-1} is the principal branch of the inverse tangent, i.e. \tan^{-1} : \mathbb{R} \to (-\pi/2 ,\pi/2). If (x_n)_{n\in\mathbb{N}} is a sequence in \mathbb{R} and...
  28. T

    First term of an infinite geometric sequence

    Homework Statement The sum of an infinite geometric sequence is 131/2, and the sum of the first three terms is 13. Find the first term. Homework Equations S∞ = a/(1-r) Sn = a-arn/(1-r) The Attempt at a Solution a/(1-r) = 131/2 a-ar3/(1-r) = 13 2a = 27-27r ...... 1 a-ar3 =...
  29. S

    What is the fourth term of an arithmetic sequence with specific given terms?

    Our 8th grade math counts team met today and I didnt know how to do this problem: The first three terms of an arithmetic sequence are p, 2p+6, and 5p-12. What is the 4th term of this sequence? Please explain how to do this. Arigato!
  30. C

    Finding the lifetime of a main sequence star.

    Homework Statement Given the following data, calculate the main sequence lifetime of the Sun (in years), assuming that all the initial mass is hydrogen and all of it is converted into helium. Mass of the Sun = M = 2x1030kg Luminosity of the Sun = L = 4x1032W Energy released in the...
  31. A

    Constructing a Sequence to Show the Existence of a Limit

    Hi, Homework Statement V is a non-empty, upper bounded subset of R. Show that a sequence (v_n)_{n \geq 0} in V exists such that: 1)v_0 \leq v_1 \leq ... and 2) the limit of the sequence is sup V. (Hint: use a recursive construction) Homework Equations The Attempt at a Solution...
  32. A

    Convergence of the Sequence An = √(2^n + 3^n)

    If an = \sqrt[n]{2^n+3^n} does the sequence converge? Prove your assertion. I have no idea where to start with this problem. It does have something to with \exists N such that n>N \Rightarrow |an - a| < ϵ for all ϵ>0 Can yall help me? It would be greatly appreciated.
  33. H

    Proof on Convergence of Sequence Given Info on Odd/Even Subsequences

    Homework Statement Given that limit of s_{2n} is L and limit of s_{2n+1} is L, prove that lim s_{n} is also L. Homework EquationsThe Attempt at a Solution This seems very obvious: If the even terms of a sequence approach a number and the odd terms of that sequence approach the same number...
  34. K

    Do All Bounded Monotone Sequences Converge?

    Homework Statement A bounded monotone sequence converges. Proof for bounded monotone increasing sequence and decreasing sequence. Does both them converges?Homework Equations So, I used the least upper bound and great lower bound to prove increasing sequence and decreasing sequence...
  35. F

    Sequence inequality, epsilon N argument

    Homework Statement I already have the solutions, but I am not sure what the solutions are trying to say. http://img194.imageshack.us/img194/2595/unledlvc.jpg So in I don't understand this, we have n > \frac{1}{\epsilon} and If (and I am guessing we really want this to...
  36. Astronuc

    New Madrid Earthquake Sequence Dec 1811–Feb 1812

    We're approaching the bicentennial anniversary of the largest earthquake and swarm east of the Rocky Mountains, at least in recent history. Coincidentally, Oklahoma has just had it's largest earthquake in the state's history. Bicentennial of the New Madrid Earthquake Sequence December...
  37. N

    Sequence and series - Arithmetic mean question have been breaking my head

    Homework Statement Two consecutive numbers from 1,2,3...n are removed A.M of remaining numbers is 105/4. Find n and those numbers removed .Homework Equations Answer n = 50 those numbers are 7 and 8 The Attempt at a Solution I solved this question like a few weeks ago but now it escaped my...
  38. A

    Proving Existence of Sequence Converging to x in R

    I asked this question before but I totally misunderstood what it was asking. Basically, I need to find that there exists a sequence {a_k} such that it converges to x for some x in R. Since the real numbers are equivalence classes of convergent Cauchy sequences the result seems fairly obvious...
  39. G

    Does Convergence of (sn) and (sntn) Imply (tn) Converges?

    Hello was wondering if anyone could help me prove that: Suppose (sn) converges to s not equal to 0 and ( sntn) converges to L. Prove that (tn) converges
  40. R

    Show That x(n) is a Cauchy Sequence for 0<r<1

    If 0<r<1 and |x(n+1) - x(n)| < r ^n for all n. Show that x(n) is Cauchy sequence. help please.
  41. H

    Understanding Limits: Solving Problems and Examples

    I've been trying to learn some maths by myself. A book I found starts with a section on limits. I feel that I have a decent understanding of what is written, but then, there are some problems given that I just can't figure out. I feel like I'm missing something basic. I'm not sure what I'm...
  42. T

    How Can I Prove a Sequence Converges with a Specific Limit?

    Im struggling with the concept of this basic sequence question. Let x(n) be a sequence such that lim(n->00) (nx(n)) = 0 i.e. it converges to zero... How could i show that there is an N s.t. for all n≥N : -1 < nx(n) < 1 Any tips would be great.. I don't want an answer.. I want to...
  43. S

    Is a general sequence possible for the given data?

    I finished exploring a family of functions fk(x) = {xksin(1/x) for x≠0 {0 for x=0 for an assignment in my Analysis course, and I'm supposed to determine the highest order derivative that exists and whether or not it's continuous...
  44. A

    Limit of sequence n^p/e^n as n approaches infinity

    Simple question just as the title says, but I can't remember or derive the solution for the life of me. I know that the answer is 0. I know why the answer is 0. But I need to know the mathematical derivation of the solution, and that's the part that I can't remember. So, to reiterate, how do you...
  45. R

    Prove this recursively defined sequence goes to 0

    Homework Statement Show that 2^{n^{1001}} |a_{n} - a_{\infty}| \rightarrow 0 as n \rightarrow \infty. Here, an is defined recursively by a_{1} = 1, a_{n+1} = \frac{1}{2}(a_{n}+\frac{x}{a_{n}}). I already know that a_{\infty} = \sqrt{x}.Homework Equations We are given a hint to consider...
  46. N

    Sum of Getometric Sequence with alternating signs

    Homework Statement 5^2 - 5^3 + 5^4 - ... + (-1)^k*5^k whre k is an integer with k >= 2 Homework Equations The Attempt at a Solution I know (5^(k-1) - 5^2)/2 gives you the sum if they were all positive. I tried multiplying it by (-1)^k or something but that just changes the sign. I...
  47. W

    Recursive sequence terms don't cancel

    Homework Statement The following series is a telescopic series. Find the exact sum of the series by performing a partial fraction decomposition and generalizing the formula for the nth partial sum Sn. Homework Equations The Attempt at a Solution 3n + 2 = A(n+1)(n+2) + B(n)(n+2) + C(n)(n+1)...
  48. F

    Cauchy sequence and topological problems

    [PLAIN]http://img805.imageshack.us/img805/1575/photo0138d.jpg Hi, on thursday, i have exam of advance calculus and i could not solve two problem in study sheet given by İnstructor. By 9 question, i prove by add an subtract XnY to |XnYn-XY| and i have found that |Xn(Yn-Y)+...
  49. L

    Definition of a limit of a sequence

    Homework Statement Use the definition of a limit to prove that lim [(1+an)-1] = 1/2 if lim an = 1. Homework Equations (\forall\epsilon>0)(\existsN\inN)(n\geqN \Rightarrow|an-L|<\epsilon) The Attempt at a Solution Let \epsilon be arbitrary. Since lim an exists, \existsN\inN such...
  50. S

    Convergence of a Cauchy sequence

    Since I don't know how to use latex I have posed my question in word file. Yours help is greatly appreciated.
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