%I #22 Aug 21 2023 11:16:54
%S 9,1,3,5,4,5,4,5,7,6,4,2,6,0,0,8,9,5,5,0,2,1,2,7,5,7,1,9,8,5,3,1,7,1,
%T 7,7,9,4,0,8,1,0,4,5,9,3,7,7,4,7,4,5,4,5,0,6,0,9,9,9,7,8,8,0,6,5,1,1,
%U 4,8,8,2,1,0,2,6,3,1,2,7,1,6,8,1,7,8,4,0,0,0,8,9,3,2,9,9,9,9,4
%N Decimal expansion of sine of 66 degrees.
%C A quartic number with denominator 2. - _Charles R Greathouse IV_, Aug 27 2017
%H Ivan Panchenko, <a href="/A019875/b019875.txt">Table of n, a(n) for n = 0..1000</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Exact_trigonometric_constants">Exact trigonometric constants</a>
%H <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>
%F Equals cos(2*Pi/15) = 2*A019887^2 - 1 = 1 - 2*A019821^2. - _R. J. Mathar_, Jun 18 2006
%F Equals 2*A019842*A019866. - _R. J. Mathar_, Jan 17 2021
%e 0.913545457...
%t RealDigits[N[Cos[2*Pi/15], 110]][[1]] (* _Wesley Ivan Hurt_, Dec 27 2021 *)
%o (PARI) cos(2*Pi/15) \\ _Charles R Greathouse IV_, Aug 27 2017
%Y Cf. A019821, A019842, A019866, A019887.
%K nonn,cons
%O 0,1
%A _N. J. A. Sloane_