A019851 Decimal expansion of sine of 42 degrees.

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

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• changed

Comments

This sequence is also decimal expansion of cosine of 48 degrees. - Mohammad K. Azarian, Jun 29 2013

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

Examples

			0.6691306...
		

Links

• Ivan Panchenko, Table of n, a(n) for n = 0..1000
• Wikipedia, Exact trigonometric constants
• Index entries for algebraic numbers, degree 4

Crossrefs

Cf. A019857, A019887, A019830, A019878.

Programs

PARI

sin(7/30*Pi) \\ Charles R Greathouse IV, Nov 05 2017

Formula

Equals cos(4*Pi/15) = (sqrt(5)-1)*(sqrt(3)*sqrt(5+2*sqrt(5))-1)/8 = 8*A019887^4 -8*A019887^2 + 1 = sqrt(1-A019857^2). - R. J. Mathar, Jun 18 2006

Equals 2*A019830*A019878. - R. J. Mathar, Jan 17 2021

A root of 16*x^4-8*x^3-16*x^2+8*x+1 =0. - R. J. Mathar, Aug 31 2025