A019849 Decimal expansion of sine of 40 degrees.

6, 4, 2, 7, 8, 7, 6, 0, 9, 6, 8, 6, 5, 3, 9, 3, 2, 6, 3, 2, 2, 6, 4, 3, 4, 0, 9, 9, 0, 7, 2, 6, 3, 4, 3, 2, 9, 0, 7, 5, 5, 9, 8, 8, 4, 2, 0, 5, 6, 8, 1, 7, 9, 0, 3, 2, 4, 9, 7, 7, 2, 5, 4, 6, 7, 1, 1, 1, 2, 8, 3, 6, 2, 4, 0, 9, 5, 8, 6, 3, 9, 7, 1, 0, 4, 8, 8, 2, 2, 7, 7, 1, 7, 5, 9, 4, 3, 5, 1

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• changed

Comments

This sequence is also the decimal expansion of cosine of 50 degrees. - Mohammad K. Azarian, Jun 29 2013

A sextic number with denominator 2. - Charles R Greathouse IV, Nov 05 2017

Examples

			0.642787609...
		

Links

• Ivan Panchenko, Table of n, a(n) for n = 0..1000
• Index entries for algebraic numbers, degree 6.

Programs

Mathematica

RealDigits[ Sin[ 2Pi/9], 10, 111][[1]] (* Robert G. Wilson v, Feb 16 2011 *)
RealDigits[Sin[40 Degree],10,120][[1]] (* Harvey P. Dale, Mar 27 2015 *)

PARI

sin(2/9*Pi) \\ Charles R Greathouse IV, Nov 05 2017

PARI

polrootsreal(64*x^6-96*x^4+36*x^2-3)[5] \\ Charles R Greathouse IV, Feb 05 2025

Formula

Equals cos(5*Pi/18) = 2F1(11/12,1/12;1/2;3/4) / 2. - R. J. Mathar, Oct 27 2008

Equals 2*A019829*A019879. - R. J. Mathar, Jan 17 2021

A root of 64*x^6 - 96*x^4 + 36*x^2 - 3. - R. J. Mathar, Aug 29 2025