%I
%S 9,3,0,8,3,8,9,0,7,1,3,2,2,3,2,4,8,2,7,8,4,5,4,0,7,3,6,3,0,9,7,3,4,8,
%T 4,9,1,1,8,1,7,8,7,4,5,9,0,1,8,4,4,8,8,1,2,2,0,4,5,3,7,8,3,9,1,2,0,6,
%U 6,6,4,7,6,2,7,3,4,3,2,2,2,7,2,4,3,1,5,9,0,5,7,5,1,5,4,1,1,5,5,7
%N Decimal expansion of 2*sin(Pi/675).
%C This constant appears in a historic problem posed by Adriaan van Roomen (Adrianus Romanus) in his Ideae mathematicae from 1593, solved by Viète. See the Havil reference, problem 4, pp. 6974. See also the comments, references and links in A302711.
%C The present identity is R(45, 2*sin(Pi/675)) = 2*sin(Pi/15) = A272534 = 0.415823381635518..., with a special case of monic Chebyshev polynomials of the first kind, named R, given in A127672.
%D Julian Havil, The Irrationals, A Story of the Numbers You Can't Count On, Princeton University Press, Princeton and Oxford, 2012, pp. 6974.
%H <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>
%F This constant is 2*sin(Pi/675).
%e 0.0093083890713223248278454073630973484911817874590184488122045378391206664762...
%t RealDigits[2 Sin[Pi/675], 10, 111][[1]] (* _Robert G. Wilson v_, Apr 29 2018 *)
%o (PARI) 2*sin(Pi/675) \\ _Altug Alkan_, May 01 2018
%Y Cf. A127672, A272534, A302711.
%K nonn,cons,easy
%O 2,1
%A _Wolfdieter Lang_, Apr 29 2018
