A019821 Decimal expansion of sine of 12 degrees.

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

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• changed

Comments

An algebraic number of degree 8 and denominator 2. - Charles R Greathouse IV, Aug 27 2017

Examples

			0.20791169...
		

Links

• Ivan Panchenko, Table of n, a(n) for n = 0..1000
• Wikipedia, Exact trigonometric constants
• Index entries for algebraic numbers, degree 8

Crossrefs

Cf. A019815, A019887, A019893.

Programs

Mathematica

RealDigits[N[Sin[Pi/15], 110]][[1]] (* Wesley Ivan Hurt, Dec 27 2021 *)

PARI

sin(Pi/15) \\ Charles R Greathouse IV, Aug 27 2017

Formula

Equals sin(Pi/15) = sqrt(1-A019887^2) = (sqrt(5)-1)*(sqrt(5+2*sqrt(5)) - sqrt(3))/8. - R. J. Mathar, Jun 18 2006

Equals 2*A019815*A019893. - R. J. Mathar, Jan 17 2021

Smallest positive of the 8 real-valued roots of 256*x^8-448*x^6+224*x^4-32*x^2+1 =0. (Other A019893, A019833, A019857)- R. J. Mathar, Aug 31 2025