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In [[complex analysis]], '''Gauss's continued fraction''' is a particular class of [[generalized continued fraction|continued fractions]] derived from [[hypergeometric function]]s. It was one of the first analytic continued fractions known to mathematics, and it can be used to represent several important [[elementary function]]s, as well as some of the more complicated [[transcendental function]]s. | |||
==History== | |||
[[Johann Heinrich Lambert|Lambert]] published several examples of continued fractions in this form in 1768, and both [[Leonhard Euler|Euler]] and [[Joseph Louis Lagrange|Lagrange]] investigated similar constructions,<ref>Jones & Thron (1980) p. 5</ref> but it was [[Carl Friedrich Gauss]] who utilized the clever algebraic trick described in the next section to deduce the general form of this continued fraction, in 1813.<ref>C. F. Gauss (1813), [http://books.google.com/books?id=uDMAAAAAQAAJ ''Werke'', vol. 3] pp. 134-138.</ref> | |||
Although Gauss gave the form of this continued fraction, he did not give a proof of its convergence properties. [[Bernhard Riemann]]<ref>B. Riemann (1863), "Sullo svolgimento del quoziente di due serie ipergeometriche in frazione continua infinita" in ''Werke''. pp. 400-406. (Posthumous fragment).</ref> and L.W. Thomé<ref>L. W. Thomé (1867), "Über die Kettenbruchentwicklung des Gauß'schen Quotienten ...," ''Jour. für Math.'' vol. 67 pp. 299-309.</ref> obtained partial results, but the final word on the region in which this continued fraction converges was not given until 1901, by [[Edward Burr Van Vleck]].<ref>E. B. Van Vleck (1901), "On the convergence of the continued fraction of Gauss and other continued fractions." ''Annals of Mathematics'', vol. 3 pp. 1-18.</ref> | |||
==Derivation== | |||
Let <math>f_0, f_1, f_2, \dots</math> be a sequence of analytic functions so that | |||
:<math>f_{i-1} - f_i = k_i\,z\,f_{i+1}</math> | |||
for all <math>i > 0</math>, where each <math>k_i</math> is a constant. | |||
Then | |||
:<math>\frac{f_{i-1}}{f_i} = 1 + k_i z \frac{f_{i+1}}{{f_i}},\, \frac{f_i}{f_{i-1}} = \frac{1}{1 + k_i z \frac{f_{i+1}}{{f_i}}}</math>. | |||
Setting <math>g_i = f_i / f_{i-1}</math>, | |||
:<math>g_i = \frac{1}{1 + k_i z g_{i+1}}</math>, | |||
So | |||
:<math>g_1 = \frac{f_1}{f_0} = \cfrac{1}{1 + k_1 z g_2} = \cfrac{1}{1 + \cfrac{k_1 z}{1 + k_2 z g_3}} | |||
= \cfrac{1}{1 + \cfrac{k_1 z}{1 + \cfrac{k_2 z}{1 + k_3 z g_4}}} = \dots\ </math>. | |||
Repeating this ad infinitum produces the continued fraction expression | |||
:<math>\frac{f_1}{f_0} = \cfrac{1}{1 + \cfrac{k_1 z}{1 + \cfrac{k_2 z}{1 + \cfrac{k_3 z}{1 + {}\ddots}}}}</math> | |||
In Gauss's continued fraction, the functions <math>f_i</math> are hypergeometric functions of the form <math>{}_0F_1</math>, <math>{}_1F_1</math>, and <math>{}_2F_1</math>, and the equations <math>f_{i-1} - f_i = k_i z f_{i+1}</math> arise as identities between functions where the parameters differ by integer amounts. These identities can be proved in several ways, for example by expanding out the series and comparing coefficients, or by taking the derivative in several ways and eliminating it from the equations generated. | |||
===The series <sub>0</sub>F<sub>1</sub>=== | |||
The simplest case involves | |||
:<math>\,_0F_1(;a;z) = 1 + \frac{1}{a\,1!}z + \frac{1}{a(a+1)\,2!}z^2 + \frac{1}{a(a+1)(a+2)\,3!}z^3 + \cdots\ </math>. | |||
Starting with the identity | |||
:<math>\,_0F_1(;a-1;z)-\,_0F_1(;a;z) = \frac{z}{a(a-1)}\,_0F_1(;a+1;z)</math>, | |||
we may take | |||
:<math>f_i = {}_0F_1(;a+i;z),\,k_i = \tfrac{1}{(a+i)(a+i-1)}</math>, | |||
giving | |||
:<math>\frac{\,_0F_1(a+1;z)}{\,_0F_1(a;z)} = \cfrac{1}{1 + \cfrac{\frac{1}{a(a+1)}z} | |||
{1 + \cfrac{\frac{1}{(a+1)(a+2)}z}{1 + \cfrac{\frac{1}{(a+2)(a+3)}z}{1 + {}\ddots}}}}</math> | |||
or | |||
:<math>\frac{\,_0F_1(a+1;z)}{a\,_0F_1(a;z)} = \cfrac{1}{a + \cfrac{z} | |||
{(a+1) + \cfrac{z}{(a+2) + \cfrac{z}{(a+3) + {}\ddots}}}}</math>. | |||
This expansion converges to the meromorphic function defined by the ratio of the two convergent series (provided, of course, that ''a'' is neither zero nor a negative integer). | |||
===The series <sub>1</sub>F<sub>1</sub>=== | |||
The next case involves | |||
:<math>{}_1F_1(a;b;z) = 1 + \frac{a}{b\,1!}z + \frac{a(a+1)}{b(b+1)\,2!}z^2 + \frac{a(a+1)(a+2)}{b(b+1)(b+2)\,3!}z^3 + \dots</math> | |||
for which the two identities | |||
:<math>\,_1F_1(a;b-1;z)-\,_1F_1(a+1;b;z) = \frac{(a-b+1)z}{b(b-1)}\,_1F_1(a+1;b+1;z)</math> | |||
:<math>\,_1F_1(a;b-1;z)-\,_1F_1(a;b;z) = \frac{az}{b(b-1)}\,_1F_1(a+1;b+1;z)</math> | |||
are used alternately. | |||
Let | |||
:<math>f_0(z) = \,_1F_1(a;b;z)</math>, | |||
:<math>f_1(z) = \,_1F_1(a+1;b+1;z)</math>, | |||
:<math>f_2(z) = \,_1F_1(a+1;b+2;z)</math>, | |||
:<math>f_3(z) = \,_1F_1(a+2;b+3;z)</math>, | |||
:<math>f_4(z) = \,_1F_1(a+2;b+4;z)</math>, | |||
etc. | |||
This gives <math>f_{i-1} - f_i = k_i z f_{i+1}</math> where <math>k_1=\tfrac{a-b}{b(b+1)}, k_2=\tfrac{a+1}{(b+1)(b+2)}, k_3=\tfrac{a-b-1}{(b+2)(b+3)}, k_4=\tfrac{a+2}{(b+3)(b+4)}</math>, producing | |||
:<math>\frac{{}_1F_1(a+1;b+1;z)}{{}_1F_1(a;b;z)} = \cfrac{1}{1 + \cfrac{\frac{a-b}{b(b+1)} z}{1 + \cfrac{\frac{a+1}{(b+1)(b+2)} z}{1 + \cfrac{\frac{a-b-1}{(b+2)(b+3)} z}{1 + \cfrac{\frac{a+2}{(b+3)(b+4)} z}{1 + {}\ddots}}}}}</math> | |||
or | |||
:<math>\frac{{}_1F_1(a+1;b+1;z)}{b{}_1F_1(a;b;z)} = \cfrac{1}{b + \cfrac{(a-b) z}{(b+1) + \cfrac{(a+1) z}{(b+2) + \cfrac{(a-b-1) z}{(b+3) + \cfrac{(a+2) z}{(b+4) + {}\ddots}}}}}</math> | |||
Similarly | |||
:<math>\frac{{}_1F_1(a;b+1;z)}{{}_1F_1(a;b;z)} = \cfrac{1}{1 + \cfrac{\frac{a}{b(b+1)} z}{1 + \cfrac{\frac{a-b-1}{(b+1)(b+2)} z}{1 + \cfrac{\frac{a+1}{(b+2)(b+3)} z}{1 + \cfrac{\frac{a-b-2}{(b+3)(b+4)} z}{1 + {}\ddots}}}}}</math> | |||
or | |||
:<math>\frac{{}_1F_1(a;b+1;z)}{b{}_1F_1(a;b;z)} = \cfrac{1}{b + \cfrac{a z}{(b+1) + \cfrac{(a-b-1) z}{(b+2) + \cfrac{(a+1) z}{(b+3) + \cfrac{(a-b-2) z}{(b+4) + {}\ddots}}}}}</math> | |||
Since <math>{}_1F_1(0;b;z)=1</math>, setting ''a'' to 0 and replacing ''b'' + 1 with ''b'' in the first continued fraction gives a simplified special case: | |||
:<math>{}_1F_1(1;b;z) = \cfrac{1}{1 + \cfrac{-z}{b + \cfrac{z}{(b+1) + \cfrac{-b z}{(b+2) + \cfrac{2z}{(b+3) + \cfrac{-(b+1)z}{(b+4) + {}\ddots}}}}}}</math> | |||
===The series <sub>2</sub>F<sub>1</sub>=== | |||
The final case involves | |||
:<math>{}_2F_1(a,b;c;z) = 1 + \frac{ab}{c\,1!}z + \frac{a(a+1)b(b+1)}{c(c+1)\,2!}z^2 + \frac{a(a+1)(a+2)b(b+1)(b+2)}{c(c+1)(c+2)\,3!}z^3 + \dots\,</math>. | |||
Again, two identities are used alternately. | |||
:<math>\,_2F_1(a,b;c-1;z)-\,_2F_1(a+1,b;c;z) = \frac{(a-c+1)bz}{c(c-1)}\,_2F_1(a+1,b+1;c+1;z)</math>, | |||
:<math>\,_2F_1(a,b;c-1;z)-\,_2F_1(a,b+1;c;z) = \frac{(b-c+1)az}{c(c-1)}\,_2F_1(a+1,b+1;c+1;z)</math>. | |||
These are essentially the same identity with ''a'' and ''b'' interchanged. | |||
Let | |||
:<math>f_0(z) = \,_2F_1(a,b;c;z)</math>, | |||
:<math>f_1(z) = \,_2F_1(a+1,b;c+1;z)</math>, | |||
:<math>f_2(z) = \,_2F_1(a+1,b+1;c+2;z)</math>, | |||
:<math>f_3(z) = \,_2F_1(a+2,b+1;c+3;z)</math>, | |||
:<math>f_4(z) = \,_2F_1(a+2,b+2;c+4;z)</math>, | |||
etc. | |||
This gives <math>f_{i-1} - f_i = k_i z f_{i+1}</math> where <math>k_1=\tfrac{(a-c)b}{c(c+1)}, | |||
k_2=\tfrac{(b-c-1)(a+1)}{(c+1)(c+2)}, k_3=\tfrac{(a-c-1)(b+1)}{(c+2)(c+3)}, k_4=\tfrac{(b-c-2)(a+2)}{(c+3)(c+4)}</math>, producing | |||
:<math>\frac{{}_2F_1(a+1,b;c+1;z)}{{}_2F_1(a,b;c;z)} = \cfrac{1}{1 + \cfrac{\frac{(a-c)b}{c(c+1)} z}{1 + \cfrac{\frac{(b-c-1)(a+1)}{(c+1)(c+2)} z}{1 + \cfrac{\frac{(a-c-1)(b+1)}{(c+2)(c+3)} z}{1 + \cfrac{\frac{(b-c-2)(a+2)}{(c+3)(c+4)} z}{1 + {}\ddots}}}}}</math> | |||
or | |||
:<math>\frac{{}_2F_1(a+1,b;c+1;z)}{c{}_2F_1(a,b;c;z)} = \cfrac{1}{c + \cfrac{(a-c)b z}{(c+1) + \cfrac{(b-c-1)(a+1) z}{(c+2) + \cfrac{(a-c-1)(b+1) z}{(c+3) + \cfrac{(b-c-2)(a+2) z}{(c+4) + {}\ddots}}}}}</math> | |||
Since <math>{}_2F_1(0,b;c;z)=1</math>, setting ''a'' to 0 and replacing ''c'' + 1 with ''c'' gives a simplified special case of the continued fraction: | |||
:<math>{}_2F_1(1,b;c;z) = \cfrac{1}{1 + \cfrac{-b z}{c + \cfrac{(b-c) z}{(c+1) + \cfrac{-c(b+1) z}{(c+2) + \cfrac{2(b-c-1) z}{(c+3) + \cfrac{-(c+1)(b+2) z}{(c+4) + {}\ddots}}}}}}</math> | |||
<!-- These yield other c.f.'s | |||
:<math>\,_1F_1(a+1;b;z)-\,_1F_1(a;b;z) = \frac{z}{b}\,_1F_1(a+1;b+1;z)</math> | |||
:<math>\,_2F_1(a+1,b;c;z)-\,_2F_1(a,b;c;z) = \frac{bz}{c}\,_2F_1(a+1,b+1;c+1;z)</math> | |||
:<math>\,_2F_1(a+1,b;c;z)-\,_2F_1(a,b+1;c;z) = \frac{(b-a)z}{c}\,_2F_1(a+1,b+1;c+1;z)</math> | |||
--> | |||
==Convergence properties== | |||
In this section, the cases where one or more of the parameters is a negative integer are excluded, since in these cases either the hypergeometric series are undefined or that they are polynomials so the continued fraction terminates. Other trivial exceptions are excluded as well. | |||
In the cases <math>{}_0F_1</math> and <math>{}_1F_1</math>, the series converge everywhere so the fraction on the left hand side is a [[meromorphic function]]. The continued fractions on the right hand side will converge uniformly on any closed and bounded set that contains no [[pole (complex analysis)|poles]] of this function.<ref>Jones & Thron (1980) p. 206</ref> | |||
In the case <math>{}_2F_1</math>, the radius of convergence of the series is 1 and the fraction on the left hand side is a meromorphic function within this circle. The continued fractions on the right hand side will converge to the function everywhere inside this circle. | |||
Outside the circle, the continued fraction represents the [[analytic continuation]] of the function to the complex plane with the positive real axis, from {{math|+1}} to the point at infinity removed. In most cases {{math|+1}} is a branch point and the line from {{math|+1}} to positive infinity is a branch cut for this function. The continued fraction converges to a meromorphic function on this domain, and it converges uniformly on any closed and bounded subset of this domain that does not contain any poles.<ref>Wall, 1973 (p. 339)</ref> | |||
==Applications== | |||
===The series <sub>0</sub>''F''<sub>1</sub>=== | |||
We have | |||
:<math>\cosh(z) = \,_0F_1({\tfrac{1}{2}};{\tfrac{z^2}{4}}),</math> | |||
:<math>\sinh(z) = z\,_0F_1({\tfrac{3}{2}};{\tfrac{z^2}{4}}),</math> | |||
so | |||
:<math>\tanh(z) = \frac{z\,_0F_1({\tfrac{3}{2}};{\tfrac{z^2}{4}})}{\,_0F_1({\tfrac{1}{2}};{\tfrac{z^2}{4}})} | |||
= \cfrac{z/2}{\tfrac{1}{2} + \cfrac{\tfrac{z^2}{4}}{\tfrac{3}{2} + \cfrac{\tfrac{z^2}{4}}{\tfrac{5}{2} + \cfrac{\tfrac{z^2}{4}}{\tfrac{7}{2} + {}\ddots}}}} = \cfrac{z}{1 + \cfrac{z^2}{3 + \cfrac{z^2}{5 + \cfrac{z^2}{7 + {}\ddots}}}}.</math> | |||
This particular expansion is known as '''Lambert's continued fraction''' and dates back to 1768.<ref>Wall (1973) p. 349.</ref> | |||
It easily follows that | |||
:<math>\tan(z) = \cfrac{z}{1 - \cfrac{z^2}{3 - \cfrac{z^2}{5 - \cfrac{z^2}{7 - {}\ddots}}}}.</math> | |||
The expansion of tanh can be used to prove that ''e''<sup>''n''</sup> is irrational for every integer ''n'' (which is alas not enough to prove that ''e'' is [[Transcendental number|transcendental]]). The expansion of tan was used by both Lambert and [[Adrien-Marie Legendre|Legendre]] to [[proof that π is irrational|prove that π is irrational]]. | |||
The [[Bessel function]] <math>J_\nu</math> can be written | |||
:<math>J_\nu(z) = \frac{(\tfrac{1}{2}z)^\nu}{\Gamma(\nu+1)}\,_0F_1(;\nu+1;-\frac{z^2}{4}),</math> | |||
from which it follows | |||
:<math>\frac{J_\nu(z)}{J_{\nu-1}(z)}=\cfrac{z}{2\nu - \cfrac{z^2}{2(\nu+1) - \cfrac{z^2}{2(\nu+2) - \cfrac{z^2}{2(\nu+3) - {}\ddots}}}}.</math> | |||
These formulas are also valid for every complex ''z''. | |||
===The series <sub>1</sub>F<sub>1</sub>=== | |||
Since <math>e^z = {}_1F_1(1;1;z)</math>, <math>1/e^z = e^{-z}</math> | |||
:<math>e^z = \cfrac{1}{1 + \cfrac{-z}{1 + \cfrac{z}{2 + \cfrac{-z}{3 + \cfrac{2z}{4 + \cfrac{-2z}{5 + {}\ddots}}}}}}</math> | |||
:<math>e^z = 1 + \cfrac{z}{1 + \cfrac{-z}{2 + \cfrac{z}{3 + \cfrac{-2z}{4 + \cfrac{2z}{5 + {}\ddots}}}}}</math>. | |||
With some manipulation, this can be used to prove the simple continued fraction representation of | |||
''[[e (mathematical constant)|e]]'', | |||
:<math>e=2+\cfrac{1}{1+\cfrac{1}{2+\cfrac{1}{1+\cfrac{1}{1+\cfrac{1}{4+{}\ddots}}}}}</math> | |||
The [[error function]] erf (''z''), given by | |||
:<math> | |||
\operatorname{erf}(z) = \frac{2}{\sqrt{\pi}}\int_0^z e^{-t^2} dt, | |||
</math> | |||
can also be computed in terms of Kummer's hypergeometric function: | |||
:<math> | |||
\operatorname{erf}(z) = \frac{2z}{\sqrt{\pi}} e^{-z^2} \,_1F_1(1;{\scriptstyle\frac{3}{2}};z^2). | |||
</math> | |||
By applying the continued fraction of Gauss, a useful expansion valid for every complex number ''z'' can be obtained:<ref>Jones & Thron (1980) p. 208.</ref> | |||
:<math> | |||
\frac{\sqrt{\pi}}{2} e^{z^2} \operatorname{erf}(z) = \cfrac{z}{1 - \cfrac{z^2}{\frac{3}{2} + | |||
\cfrac{z^2}{\frac{5}{2} - \cfrac{\frac{3}{2}z^2}{\frac{7}{2} + \cfrac{2z^2}{\frac{9}{2} - | |||
\cfrac{\frac{5}{2}z^2}{\frac{11}{2} + \cfrac{3z^2}{\frac{13}{2} - | |||
\cfrac{\frac{7}{2}z^2}{\frac{15}{2} + - \ddots}}}}}}}}. | |||
</math> | |||
A similar argument can be made to derive continued fraction expansions for the [[Fresnel integral]]s, for the [[Dawson function]], and for the [[incomplete gamma function]]. A simpler version of the argument yields two useful continued fraction expansions of the [[exponential function]].<ref>See the example in the article [[Padé table]] for the expansions of ''e<sup>z</sup>'' as continued fractions of Gauss.</ref> | |||
===The series <sub>2</sub>F<sub>1</sub>=== | |||
From | |||
:<math>(1-z)^{-b}={}_1F_0(b;;z)=\,_2F_1(1,b;1;z)</math>, | |||
:<math>(1-z)^{-b} = \cfrac{1}{1 + \cfrac{-b z}{1 + \cfrac{(b-1) z}{2 + \cfrac{-(b+1) z}{3 + \cfrac{2(b-2) z}{4 + {}\ddots}}}}}</math> | |||
It is easily shown that the Taylor series expansion of [[Inverse trigonometric functions#Continued fractions for arctangent|arctan ''z'']] in a neighborhood of zero is given by | |||
:<math> | |||
\arctan z = zF({\scriptstyle\frac{1}{2}},1;{\scriptstyle\frac{3}{2}};-z^2). | |||
</math> | |||
The continued fraction of Gauss can be applied to this identity, yielding the expansion | |||
:<math> | |||
\arctan z = \cfrac{z} {1+\cfrac{(1z)^2} {3+\cfrac{(2z)^2} {5+\cfrac{(3z)^2} {7+\cfrac{(4z)^2} {9+\ddots}}}}}, | |||
</math> | |||
which converges to the principal branch of the inverse tangent function on the cut complex plane, with the cut extending along the imaginary axis from ''i'' to the point at infinity, and from −''i'' to the point at infinity.<ref>Wall (1973) p. 343. Notice that ''i'' and −''i'' are [[branch point]]s for the inverse tangent function.</ref> | |||
This particular continued fraction converges fairly quickly when ''z'' = 1, giving the value π/4 to seven decimal places by the ninth convergent. The corresponding series | |||
:<math> | |||
\frac{\pi}{4} = \cfrac{1} {1+\cfrac{1^2} {2+\cfrac{3^2} {2+\cfrac{5^2} {2+\ddots}}}} | |||
= 1 - \frac{1}{3} + \frac{1}{5} - \frac{1}{7} + - \dots | |||
</math> | |||
converges much more slowly, with more than a million terms needed to yield seven decimal places of accuracy.<ref>Jones & Thron (1980) p. 202.</ref> | |||
Variations of this argument can be used to produce continued fraction expansions for the [[natural logarithm]], the [[inverse trigonometric functions|arcsin function]], and the [[binomial series|generalized binomial series]]. | |||
==Notes== | |||
{{reflist}} | |||
==References== | |||
* {{cite book|last = Jones|first = William B.|coauthors = Thron, W. J.|title = Continued Fractions: Theory and Applications|publisher = Addison-Wesley Publishing Company|location = Reading, Massachusetts|year = 1980|pages = 198–214|isbn = 0-201-13510-8}} | |||
* {{cite book|last = Wall|first = H. S.|title = Analytic Theory of Continued Fractions|publisher = Chelsea Publishing Company|year = 1973|pages = 335–361|isbn = 0-8284-0207-8}}<br /><small>(This is a reprint of the volume originally published by D. Van Nostrand Company, Inc., in 1948.)</small> | |||
* {{MathWorld|title=Gauss's Continued Fraction|urlname=GausssContinuedFraction}} | |||
[[Category:Continued fractions]] |
Revision as of 13:10, 8 January 2014
In complex analysis, Gauss's continued fraction is a particular class of continued fractions derived from hypergeometric functions. It was one of the first analytic continued fractions known to mathematics, and it can be used to represent several important elementary functions, as well as some of the more complicated transcendental functions.
History
Lambert published several examples of continued fractions in this form in 1768, and both Euler and Lagrange investigated similar constructions,[1] but it was Carl Friedrich Gauss who utilized the clever algebraic trick described in the next section to deduce the general form of this continued fraction, in 1813.[2]
Although Gauss gave the form of this continued fraction, he did not give a proof of its convergence properties. Bernhard Riemann[3] and L.W. Thomé[4] obtained partial results, but the final word on the region in which this continued fraction converges was not given until 1901, by Edward Burr Van Vleck.[5]
Derivation
Let be a sequence of analytic functions so that
for all , where each is a constant.
Then
So
Repeating this ad infinitum produces the continued fraction expression
In Gauss's continued fraction, the functions are hypergeometric functions of the form , , and , and the equations arise as identities between functions where the parameters differ by integer amounts. These identities can be proved in several ways, for example by expanding out the series and comparing coefficients, or by taking the derivative in several ways and eliminating it from the equations generated.
The series 0F1
The simplest case involves
Starting with the identity
we may take
giving
or
This expansion converges to the meromorphic function defined by the ratio of the two convergent series (provided, of course, that a is neither zero nor a negative integer).
The series 1F1
The next case involves
for which the two identities
are used alternately.
Let
etc.
or
Similarly
or
Since , setting a to 0 and replacing b + 1 with b in the first continued fraction gives a simplified special case:
The series 2F1
The final case involves
Again, two identities are used alternately.
These are essentially the same identity with a and b interchanged.
Let
etc.
or
Since , setting a to 0 and replacing c + 1 with c gives a simplified special case of the continued fraction:
Convergence properties
In this section, the cases where one or more of the parameters is a negative integer are excluded, since in these cases either the hypergeometric series are undefined or that they are polynomials so the continued fraction terminates. Other trivial exceptions are excluded as well.
In the cases and , the series converge everywhere so the fraction on the left hand side is a meromorphic function. The continued fractions on the right hand side will converge uniformly on any closed and bounded set that contains no poles of this function.[6]
In the case , the radius of convergence of the series is 1 and the fraction on the left hand side is a meromorphic function within this circle. The continued fractions on the right hand side will converge to the function everywhere inside this circle.
Outside the circle, the continued fraction represents the analytic continuation of the function to the complex plane with the positive real axis, from Buying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
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This feature is suitable for you who need to get the tax deductions out of your PIC scheme to your property agency firm. It's endorsed that you visit the correct site for filling this tax return software. This utility must be submitted at the very least yearly to report your whole tax and tax return that you're going to receive in the current accounting 12 months. There may be an official website for this tax filling procedure. Filling this tax return software shouldn't be a tough thing to do for all business homeowners in Singapore.
A wholly owned subsidiary of SLP Worldwide, SLP Realty houses 900 associates to service SLP's fast rising portfolio of residential tasks. Real estate is a human-centric trade. Apart from offering comprehensive coaching applications for our associates, SLP Realty puts equal emphasis on creating human capabilities and creating sturdy teamwork throughout all ranges of our organisational hierarchy. Worldwide Presence At SLP International, our staff of execs is pushed to make sure our shoppers meet their enterprise and investment targets. Under is an inventory of some notable shoppers from completely different industries and markets, who've entrusted their real estate must the expertise of SLP Worldwide.
If you're looking for a real estate or Singapore property agent online, you merely need to belief your instinct. It is because you don't know which agent is sweet and which agent will not be. Carry out research on a number of brokers by looking out the internet. As soon as if you find yourself certain that a selected agent is dependable and trustworthy, you'll be able to choose to utilize his partnerise find you a house in Singapore. More often than not, a property agent is considered to be good if she or he places the contact data on his web site. This is able to imply that the agent does not thoughts you calling them and asking them any questions regarding properties in Singapore. After chatting with them you too can see them of their office after taking an appointment.
Another method by way of which you could find out whether the agent is sweet is by checking the feedback, of the shoppers, on the website. There are various individuals would publish their comments on the web site of the Singapore property agent. You can take a look at these feedback and the see whether it will be clever to hire that specific Singapore property agent. You may even get in contact with the developer immediately. Many Singapore property brokers know the developers and you may confirm the goodwill of the agent by asking the developer. is a branch point and the line from Buying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
Professional agents are readily available once you need to discover an condominium for hire in singapore In some cases, landlords will take into account you more favourably in case your agent comes to them than for those who tried to method them by yourself. You need to be careful, nevertheless, as you resolve in your agent. Ensure that the agent you are contemplating working with is registered with the IEA – Institute of Estate Brokers. Whereas it might sound a hassle to you, will probably be worth it in the end. The IEA works by an ordinary algorithm and regulations, so you'll protect yourself in opposition to probably going with a rogue agent who prices you more than they should for his or her service in finding you an residence for lease in singapore.
There isn't any deal too small. Property agents who are keen to find time for any deal even if the commission is small are the ones you want on your aspect. Additionally they present humbleness and might relate with the typical Singaporean higher. Relentlessly pursuing any deal, calling prospects even without being prompted. Even if they get rejected a hundred times, they still come again for more. These are the property brokers who will find consumers what they need eventually, and who would be the most successful in what they do. 4. Honesty and Integrity
This feature is suitable for you who need to get the tax deductions out of your PIC scheme to your property agency firm. It's endorsed that you visit the correct site for filling this tax return software. This utility must be submitted at the very least yearly to report your whole tax and tax return that you're going to receive in the current accounting 12 months. There may be an official website for this tax filling procedure. Filling this tax return software shouldn't be a tough thing to do for all business homeowners in Singapore.
A wholly owned subsidiary of SLP Worldwide, SLP Realty houses 900 associates to service SLP's fast rising portfolio of residential tasks. Real estate is a human-centric trade. Apart from offering comprehensive coaching applications for our associates, SLP Realty puts equal emphasis on creating human capabilities and creating sturdy teamwork throughout all ranges of our organisational hierarchy. Worldwide Presence At SLP International, our staff of execs is pushed to make sure our shoppers meet their enterprise and investment targets. Under is an inventory of some notable shoppers from completely different industries and markets, who've entrusted their real estate must the expertise of SLP Worldwide.
If you're looking for a real estate or Singapore property agent online, you merely need to belief your instinct. It is because you don't know which agent is sweet and which agent will not be. Carry out research on a number of brokers by looking out the internet. As soon as if you find yourself certain that a selected agent is dependable and trustworthy, you'll be able to choose to utilize his partnerise find you a house in Singapore. More often than not, a property agent is considered to be good if she or he places the contact data on his web site. This is able to imply that the agent does not thoughts you calling them and asking them any questions regarding properties in Singapore. After chatting with them you too can see them of their office after taking an appointment.
Another method by way of which you could find out whether the agent is sweet is by checking the feedback, of the shoppers, on the website. There are various individuals would publish their comments on the web site of the Singapore property agent. You can take a look at these feedback and the see whether it will be clever to hire that specific Singapore property agent. You may even get in contact with the developer immediately. Many Singapore property brokers know the developers and you may confirm the goodwill of the agent by asking the developer. to positive infinity is a branch cut for this function. The continued fraction converges to a meromorphic function on this domain, and it converges uniformly on any closed and bounded subset of this domain that does not contain any poles.[7]
Applications
The series 0F1
We have
so
This particular expansion is known as Lambert's continued fraction and dates back to 1768.[8]
It easily follows that
The expansion of tanh can be used to prove that en is irrational for every integer n (which is alas not enough to prove that e is transcendental). The expansion of tan was used by both Lambert and Legendre to prove that π is irrational.
The Bessel function can be written
from which it follows
These formulas are also valid for every complex z.
The series 1F1
With some manipulation, this can be used to prove the simple continued fraction representation of e,
The error function erf (z), given by
can also be computed in terms of Kummer's hypergeometric function:
By applying the continued fraction of Gauss, a useful expansion valid for every complex number z can be obtained:[9]
A similar argument can be made to derive continued fraction expansions for the Fresnel integrals, for the Dawson function, and for the incomplete gamma function. A simpler version of the argument yields two useful continued fraction expansions of the exponential function.[10]
The series 2F1
From
It is easily shown that the Taylor series expansion of arctan z in a neighborhood of zero is given by
The continued fraction of Gauss can be applied to this identity, yielding the expansion
which converges to the principal branch of the inverse tangent function on the cut complex plane, with the cut extending along the imaginary axis from i to the point at infinity, and from −i to the point at infinity.[11]
This particular continued fraction converges fairly quickly when z = 1, giving the value π/4 to seven decimal places by the ninth convergent. The corresponding series
converges much more slowly, with more than a million terms needed to yield seven decimal places of accuracy.[12]
Variations of this argument can be used to produce continued fraction expansions for the natural logarithm, the arcsin function, and the generalized binomial series.
Notes
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
References
- 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
(This is a reprint of the volume originally published by D. Van Nostrand Company, Inc., in 1948.)
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- ↑ Jones & Thron (1980) p. 5
- ↑ C. F. Gauss (1813), Werke, vol. 3 pp. 134-138.
- ↑ B. Riemann (1863), "Sullo svolgimento del quoziente di due serie ipergeometriche in frazione continua infinita" in Werke. pp. 400-406. (Posthumous fragment).
- ↑ L. W. Thomé (1867), "Über die Kettenbruchentwicklung des Gauß'schen Quotienten ...," Jour. für Math. vol. 67 pp. 299-309.
- ↑ E. B. Van Vleck (1901), "On the convergence of the continued fraction of Gauss and other continued fractions." Annals of Mathematics, vol. 3 pp. 1-18.
- ↑ Jones & Thron (1980) p. 206
- ↑ Wall, 1973 (p. 339)
- ↑ Wall (1973) p. 349.
- ↑ Jones & Thron (1980) p. 208.
- ↑ See the example in the article Padé table for the expansions of ez as continued fractions of Gauss.
- ↑ Wall (1973) p. 343. Notice that i and −i are branch points for the inverse tangent function.
- ↑ Jones & Thron (1980) p. 202.