For questions on continued fractions.

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Continued fractions with rational functions

Express the following rational function in continued-fraction form: $${4x^2+3x-7\over 2x^3+x^2-x+5}$$ The answer is : $${4 \over 2x- \frac{1}{2}} + { \frac{23}{8} \over ...
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2answers
182 views

Continued Fractions Approximation

I have come across continued fractions approximation but I am unsure what the steps are. For example How would you express the following rational function in continued-fraction form: $${x^2+3x+2 ...
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0answers
60 views

Proof of a Continued Fraction Identity using basic CF definition.

Two definitions (the first is informal) of continued fraction: This is the basic Continued Fraction algorithm for real numbers. Let $\alpha \in \mathbb{R}$. If $[\alpha]=\alpha$, then we are done. ...
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1answer
649 views

Calculate the continued fraction of square root

I was having difficulty understanding the algorithm to calculate Continued fraction expansion of square root. I know the process is about extracting the integer part in repeat and maintaining the ...
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3answers
145 views

Continued fractions proof?

Let $b_1=1$ and $$b_n=1+\frac{1}{1+b_{n-1}}$$ for $n\ge 2$. Note that $b_n \ge 1$ for all $n$ in $\mathbb N$. ($\mathbb N$ represents the positive integers) Show that $b_{2k-1}^2<2$ for all $k ...
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1answer
954 views

Approximating $\arctan x$ for large $|x|$

I would like to know if there is reasonably fast converging method for computing large arguments of arctan. Until now I've came across Taylor series that converges only on interval $(-1,1)$ and for ...
5
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1answer
161 views

A question about continued fractions and Gauss map

For $\alpha \in (0,1)$, write $\alpha$ as a continued fraction like $\alpha=[a_1, a_2, \ldots]$ (note that the implicit $0$th coefficient $a_0=0$ has been omitted), and let $\frac{p_n}{q_n}$ be the ...
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0answers
90 views

continued fraction multivariate normal distribution?

After searching for a while, I wonder if a continued fraction representation exists for the multivariate Mills ratio $P(Z \geq x)/\phi_Z(x)$ where $Z \tilde\, N(\mu,\Sigma)$. The representation ...
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3answers
202 views

How do I solve a Continued Fraction of solution to quadratic equation?

I know that it is possible to make a CF (continued fraction) for every number that is a solution of a quadratic equation but I don't know how. The number I'd like to write as a CF is: $$\frac{1 - ...
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0answers
134 views

Uniqueness of continued fraction representation of rational numbers

I have problems proving the uniqueness of simple continued fraction representation of rational numbers as claimed in http://en.wikipedia.org/wiki/Continued_fraction#Finite_continued_fractions. Let ...
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0answers
158 views

continued fraction to rational polynomial in maple?

In maple is there a way to convert a continued fraction into a rational polynomial? I'm using the minimax function and for a particular function I want to approximate it returns a continued fraction ...
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1answer
147 views

optimality of 2 in a continued fraction theorem

I'm giving some lectures on continued fractions to high school and college students, and I discussed the standard theorem that, for a real number $\alpha$ and integers $p$ and $q$ with $q \not= 0$, if ...
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2answers
493 views

Is the continued fraction of the square root of a base $\phi$ (golden ratio) number periodic when the continued fraction is expressed in base $\phi$?

I have been looking at concise ways to represent irrational numbers using only integers. I was thinking about base $\phi$ (golden ratio base) and how it can represent the quadratic extension of the ...
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1answer
149 views

Why is this set of continued fractions perfect?

Would somebody please explain why the set of continued fractions in this answer http://math.stackexchange.com/a/1067/20873 i.e. "the set of all irrationals with continued fractions consisting only ...
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1answer
263 views

Convergent fraction for constant $e$?

I've just learned about e. I am very much the novice and my problem is that while trying to calculate the convergent fractions for e. For instance: ...
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1answer
372 views

Are there simple algebraic operations for continued fractions?

I thought about continued fractions as a cool way to represent numbers, but also about the fact they are difficult to treat because standard algebraic operations like addition and multiplication don't ...
5
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3answers
368 views

finding the rational number which the continued fraction $[1;1,2,1,1,2,\ldots]$ represents

I'd really love your help with finding the rational number which the continued fraction $[1;1,2,1,1,2,\ldots]$ represents. With the recursion for continued fraction $( p_0=a_0, q_0=1, p_{-1}=1, ...
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2answers
113 views

Continued fraction question

I have been given an continued fraction for a number x: $$x = 1+\frac{1}{1+}\frac{1}{1+}\frac{1}{1+}\cdots$$ How can I show that $x = 1 + \frac{1}{x}$? I played around some with the first few ...
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3answers
188 views

Solution to $x=1+\frac{1}{1+\frac{1}{1+\frac{1}{1+\ldots}}}$ [duplicate]

Possible Duplicate: Why does this process, when iterated, tend towards a certain number? (the golden ratio?) Please post your favorit solution to the following Compute ...
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0answers
109 views

Finding a closed expression for a calculated value.

Sometimes, when getting some numerical results when investigating number theory sequences with a computer, I find myself suspecting that a decimal value ($a$) I have found might be a quadratic ...
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5answers
355 views

How are continued fractions useful?

On Wolfram Alpha, I see continued fractions being listed in the results. Although I understand continued fractions, and how they can be used for approximations, what is a better approximation than a ...
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1answer
1k views

What was Ramanujan's solution?

The wikipedia entry on Ramanujan contains the following passage: One of his remarkable capabilities was the rapid solution for problems. He was sharing a room with P. C. Mahalanobis who had a ...
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1answer
708 views

A new continued fraction for Apéry's constant, $\zeta(3)$?

As a background, Ramanujan also gave a continued fraction for $\zeta(3)$ as $\zeta(3) = 1+\cfrac{1}{u_1+\cfrac{1^3}{1+\cfrac{1^3}{u_2+\cfrac{2^3}{1+\cfrac{2^3}{u_3 + \ddots}}}}}\tag{1}$ where the ...
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2answers
98 views

finding the quadratic irratonality of simple continued fractions

For instance: find the quadratic irrationality of the simple continued fraction [1;2,3]. I have a handful of these problems to do, so any walk-through of one problem should give me the general idea ...
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2answers
256 views

Continued fractions

I'd really love with concluding that for given integers $a_0,a_1,...a_N$ with $a_i>0$ for $i>0$, representing the continued fraction $[a_0; a_1,....,a_N]$, with the following recursion: ...
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1answer
30 views

If $x=[a_0;a_1,a_2,\dots]$, then $|x-C_k|<1/a_k^{\text{}}q_k^2$.

How can I show that if $x=[a_0;a_1,a_2,\dots]$, then $|x-C_k|<1/a_k^{\text{}}q_k^2$ using the facts that $$\begin{align} C_k-C_{k-1}&=\frac{(-1)^{k-1}}{q_kq_{k-1}}\text{, and}\\ ...
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3answers
435 views

Equivalence of Two Different Irrational Numbers

If $\alpha$ and $\beta$ are two real numbers, we say that $\beta$ is equivalent to $\alpha$ if there are integers $a$, $b$, $c$, and $d$ such that $ad-bc=\pm1$ and $\beta=\frac{a\alpha+b}{c\alpha+d}$. ...
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1answer
47 views

Continued Fractions Convergents $C_k-C_{k-3}$

Derive a formula for $C_k-C_{k-3}$ in terms of partial quotients $a_k$ and nominal denominators $q_k$. Recall that $$C_k=\frac{p_k}{q_k}$$ where $$\begin{matrix} \begin{align} p_0&=a_0 & ...
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2answers
107 views

All Even-Numbered Convergents of a Finite Continued Fraction Are Less Than the Value

Let $x=[a_0;a_1,a_2]$ be shorthand notation for the continued fraction $$x=a_0+\frac{1}{a_1+\frac{1}{a_2}}.$$ Then every $x\in\mathbb{Q}$ can be represented as a finite continued fraction ...
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1answer
174 views

How can I find power series of $f(x)$?

$$f(x)=\dfrac{1}{1+\dfrac{x}{1+\dfrac{x^2}{1+\dfrac{x^3}{1+\dfrac{x^4}{\ddots}}}}}$$ How can a power series be found given the continued fraction $f(x)$? I'm trying to find $f(x) ...
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2answers
103 views

Narrowing a Stern-Brocot tree

Say I only wanted to enumerate the rational numbers between 0 and $a$. Is there a way to "narrow" a Stern-Brocot tree to provide this? I tried keeping my left bound at "$\frac{0}{1}$" and setting my ...
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0answers
75 views

Is that observation really a property of the log of coefficients of continued fractions (example: cf(log(3)/log(2))

I'm again looking at the problem of approximation of perfect powers of 2 to that of 3 (I assume $\small q_N = 2^S / 3^N \gt 1 $) and specifically using the continued fraction representation of $\small ...
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2answers
178 views

Calculating the continued fraction of $\sqrt{47}$ using a different result

I have calculated the continued fraction of $\alpha=\frac{6+\sqrt{47}}{11}$ which equals $\overline{[1,5,1,12]}$. Now I am asked to calculated the cont. fraction of $\sqrt{47}$ using this result. I am ...
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1answer
89 views

Calculate the quadratic irrational number given by a certain periodic cont. fraction

Calculate the quadratic irrational number $\alpha$ given by the periodic continued fraction $\alpha = \overline{ [1,2,1] } $. To be honest I am not sure how to tackle this one. I know the algorithm ...
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2answers
81 views

Unique continued fraction

If $x$ is a uniformly random number in $[0,1]$, what distribution should the $n$-th term in its continued fraction expansion follow? What is the expected vale of $a_n$ in $[a_0;a_1,a_2,\dots]$? Here ...
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1answer
95 views

Do best lower approximations of a quadratic irrational always form a linear recurrence sequence?

Let $\theta$ be an irrational number and let $$ {\cal L}= \bigg\lbrace (a,b) \in {\mathbb Z} \times {\mathbb N}^{*} \bigg| \frac{a}{b} \leq \theta \bigg\rbrace $$ and $$ {\cal B}= \bigg\lbrace ...
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0answers
189 views

On the continued fraction of $e$

The following question comes up during analysis of Padé approximants to $e^x$ (see my related question in MathOverflow for more background). Recall that the continued fraction expansion of $e$ is $$ e ...
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1answer
533 views

Direct proof that for a prime $p$ if $p\equiv 1 \bmod 4$ then $l(\sqrt{p})$ is odd.

Definition: Assume $p$ is a prime. $l(\sqrt{p})=$ length of period in simple continued fraction expansion of $\sqrt{p}$. The standard proof of this uses the following: $p$ is a prime implies $p ...
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3answers
178 views

What do High-Water Marks in Continued Fractions mean?

While reading through several articles concerned with mathematical constants, I kept on finding things like this: The continued fraction for $\mu$(Soldner's Constant) is given by $\left[1, 2, 4, ...
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0answers
142 views

How to prove that this series $f(z)=1+\sum_{k=1}^{\infty}2^{-k z}$ converges using the theory of continued fractions?

Consider the following series \begin{equation} f(z)=1+\sum_{k=1}^{\infty}\frac{1}{2^{k z}} =1+ \sum_{n=1}^{\infty}\left( \prod_{k=1}^{n}\frac{1}{2^{z}} \right) \end{equation} Using Euler's continued ...
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4answers
553 views

How to detect when continued fractions period terminates

I'm doing continued fractions arithmetic. Is there a method to detect when a continued fractions period terminates? Let me give you an example: $\sqrt{2} = [1; \overline{2}]$, $\sqrt{7} = [2; ...
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1answer
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Converting a square root into a simple continued fraction

One can convert a square root $\sqrt{n}$ into a continued fraction $[a_0; \overline{a_1, a_2, \dots , a_k}]$ following the algebraic algorithm explained here: ...
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1answer
68 views

Continued Fraction: Why do we get with $\gamma \in \mathbb{R}\setminus \mathbb{Q}$ the CF $\frac{1}{\gamma}=\langle0;a_0,a_1,\dotsc\rangle$

I have a question concerning continued fractions: If we have $\gamma \in \mathbb{R} \setminus \mathbb{Q}$ and $\gamma=\langle a_0;a_1,a_2,\dotsc\rangle$. Why do we get $$\frac1\gamma = \langle ...
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0answers
277 views

continued fractions and convex hulls

If I remember correctly, there is a nice correspondence between continued fractions and convex hulls of lattice points in the plane. If $\theta>0$ is the slope of a line in $\mathbb{R}^2$ passing ...
3
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3answers
492 views

Continued fraction: Show $\sqrt{n^2+2n}=[n; \overline{1,2n}]$

I have to show the following identity ($n \in \mathbb{N}$): $$\sqrt{n^2+2n}=[n; \overline{1,2n}]$$ I had a look about the procedure for $\sqrt{n}$ on Wiki, but I don't know how to transform it to ...
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0answers
205 views

How to simplify $\newcommand{\bigk}{\mathop{\vcenter{\hbox{K}}}}\prod_{p\in\mathbb{P}}\left(1+\bigk_{k=1}^{\infty }\frac{f_k(s)}{g_k(s)}\right)^{-1}$

I'd like to simplify $$\newcommand{\bigk}{\mathop{\huge\vcenter{\hbox{K}}}}B(s)=\prod_{p\in\mathbb{P}}\left(1+\bigk_{k=1}^{\infty }\frac{f_{k}(s)}{f_{k}(s)}\right)^{-1}$$ to something of the form ...
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1answer
143 views

Reciprocal of a continued fraction

I have to prove the following: Let $\alpha=[a_0;a_1,a_2,...,a_n]$ and $\alpha>0$, then $\dfrac1{\alpha}=[0;a_0,a_1,...,a_n]$ I started with ...
2
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1answer
84 views

Show $p(n)=n(p_{n-1}+p_{n-2})+(n-1)p_{n-3}+(n-2)p_{n-4}+…+3p_1+2p_0+2$

I have to show the following: Let $N_k=\frac{p_k}{q_k}$ with $\alpha=\langle 1;2,3,4,...,n,n+1\rangle$ and $n \in \mathbb{N}$. Then $\forall n \in \mathbb{N}$ with $n\geq 3$, ...
5
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2answers
171 views

A continued fraction involving composite numbers

What is the limit of the continued fraction whose partial denominators are the composites?
2
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2answers
230 views

Taking the negative of a continued fraction

If I have a continued fraction for an irrational number $z= \langle a_0;a_1,a_2,a_3,\ldots\rangle$ it seems that $(-1)*z = \langle-a_0;-a_1,-a_2,-a_3,\ldots\rangle$. Is this true? In general, if you ...