%I #10 Nov 08 2021 14:37:43
%S 6,4,9,5,4,3,3,9,3,4,9,2,5,9,8,0,9,8,2,1,5,1,2,4,6,7,3,8,8,0,6,8,4,9,
%T 4,0,7,0,4,7,6,8,9,6,3,3,5,3,7,9,7,4,3,8,3,8,9,2,1,1,3,9,2,3,4,6,7,5,
%U 9,3,4,6,6,1,6,5,8,2,7,4,5,7,2,4,7,6,1,0,2,4,7,6
%N Decimal expansion of 2*(sin(Pi/38) - sin((7*Pi)/38) + cos((4*Pi)/19)).
%F Equals (-1)^(4/19) - (-1)^(6/19) + (-1)^(9/19) - (-1)^(10/19) + (-1)^(13/19) - (-1)^(15/19).
%e 0.64954339349259809821512467388068494070476896335379743838921136...
%p Digits := 120: (-1)^(4/19) - (-1)^(6/19) + (-1)^(9/19) - (-1)^(10/19) + (-1)^(13/19) - (-1)^(15/19): evalf(%)*10^99: ListTools:-Reverse(convert(floor(%), base, 10));
%t RealDigits[2*(Sin[Pi/38] - Sin[7*Pi/38] + Cos[4*Pi/19]), 10, 100][[1]] (* _Amiram Eldar_, Nov 08 2021 *)
%o (PARI) 2*(sin(Pi/38) - sin((7*Pi)/38) + cos((4*Pi)/19)) \\ _Michel Marcus_, Nov 08 2021
%K nonn,cons
%O 0,1
%A _Peter Luschny_, Nov 08 2021