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A115365 Decimal expansion of smallest positive root of tan(x) = x. 15
4, 4, 9, 3, 4, 0, 9, 4, 5, 7, 9, 0, 9, 0, 6, 4, 1, 7, 5, 3, 0, 7, 8, 8, 0, 9, 2, 7, 2, 8, 0, 3, 2, 2, 0, 8, 2, 2, 1, 5, 5, 8, 3, 8, 7, 2, 2, 9, 0, 0, 4, 0, 8, 0, 2, 8, 9, 5, 8, 2, 3, 9, 6, 1, 9, 2, 6, 9, 5, 0, 3, 1, 4, 5, 9, 7, 1, 0, 4, 0, 9, 8, 7, 2, 9, 0, 5, 7, 8, 0, 9, 4, 5, 5, 8, 7, 9, 6, 9, 1, 5, 2, 1, 7, 6 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Location (for x>0) of the first negative lobe of sinc(x) = sin(x)/x, where sinc(x) attains its absolute minimum of -0.217233628... The function sinc(x) is important in spectral theory (transient data truncation artifacts). - Stanislav Sykora, Mar 05 2012

Also the first root of the sinc(3,x) function, that is, the radial component of the 3D Fourier transform of 3-dimensional unit sphere. Also the first root of the spherical Bessel function of the 1st kind, j_1(x). - Stanislav Sykora, Nov 14 2013

REFERENCES

M. Abramowitz, I. A. Stegun, Editors, Handbook of Mathematical Functions, Dover Publications, 1965, Chapter 10.

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

Mohammad K. Azarian, On the Fixed Points of a Function and the Fixed Points of its Composite Functions, International Journal of Pure and Applied Mathematics, Vol. 46, No. 1, 2008, pp. 37-44.  Mathematical Reviews, MR2433713 (2009c:65129), March 2009.  Zentralblatt MATH, Zbl 1160.65015.

Mohammad K. Azarian, Fixed Points of a Quadratic Polynomial, Problem 841, College Mathematics Journal, Vol. 38, No. 1, January 2007, p. 60.

Mohammad K. Azarian, Solution to Fixed Points of a Quadratic Polynomial, Problem 841, College Mathematics Journal Vol. 39, No. 1, January 2008, pp. 66-67.

Stanislav Sykora, K-Space Images of n-Dimensional Spheres and Generalized Sinc Functions

Eric Weisstein's World of Mathematics, Tangent

Eric Weisstein's World of Mathematics, Tanc Function

EXAMPLE

4.4934094579090641753...

MAPLE

Digits:=200; fsolve(x*cos(x)-sin(x), x, 4..5);

MATHEMATICA

RealDigits[FindRoot[Tan[x]==x, {x, 4}, WorkingPrecision->128][[1, 2]]][[1]] (* Robert G. Wilson v, Mar 05 2012 *)

RealDigits[BesselJZero[3/2, 1], 10, 100][[1]] (* Vladimir Reshetnikov, May 13 2016 *)

PROG

(PARI) solve(x=4, 4.5, tan(x)-x) \\ Charles R Greathouse IV, Jun 10 2012

CROSSREFS

Cf. A102015 (continued fraction), A213053 (amplitude at x).

Cf. A062546, A224196, A207528, A243108, A245333.

Sequence in context: A246668 A021073 A021961 * A263491 A272427 A068340

Adjacent sequences:  A115362 A115363 A115364 * A115366 A115367 A115368

KEYWORD

nonn,cons

AUTHOR

Eric W. Weisstein, Jan 21 2006

EXTENSIONS

Mathematica program corrected by Harvey P. Dale, Mar 22 2012

STATUS

approved

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Last modified December 1 16:44 EST 2021. Contains 349430 sequences. (Running on oeis4.)