%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. 69-74. 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. 69-74.
%H <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>
%F This constant is 2*sin(Pi/675).
%t RealDigits[2 Sin[Pi/675], 10, 111][] (* _Robert G. Wilson v_, Apr 29 2018 *)
%o (PARI) 2*sin(Pi/675) \\ _Altug Alkan_, May 01 2018
%Y Cf. A127672, A272534, A302711.
%A _Wolfdieter Lang_, Apr 29 2018