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 A019845 Decimal expansion of sine of 36 degrees. 8

%I

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

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

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

%N Decimal expansion of sine of 36 degrees.

%C This sequence is also decimal expansion of cosine of 54 degrees. - _Mohammad K. Azarian_, Jun 29 2013

%C The ratio of side to longer diagonal for any golden rhombus (see A019881). - _Rick L. Shepherd_, Apr 10 2017

%H Zak Seidov, <a href="/A019845/b019845.txt">Table of n, a(n) for n = 0..999</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Exact_trigonometric_constants">Exact trigonometric constants</a>

%F sin 36 degrees = sin Pi/5 radians = sqrt((1/8)(5 - sqrt(5))).

%F Equals A019881/A001622. - _Rick L. Shepherd_, Apr 10 2017

%F This constant is (1/2)*A182007. - _Wolfdieter Lang_, May 08 2018

%e sin 36 degrees = 0.587785252292473129168705954639...

%t RealDigits[Sin[Pi/5], 10, 100][[1]] (* _Alonso del Arte_, Sep 19 2017 *)

%t RealDigits[Sin[36 Degree],10,120][[1]] (* _Harvey P. Dale_, Aug 14 2018 *)

%o (PARI) sin(Pi/5) \\ _Michel Marcus_, Apr 25 2015

%o (PARI) cos(3*Pi/10) \\ _Rick L. Shepherd_, Apr 10 2017

%o (PARI) real(I^(3/5)) \\ _Rick L. Shepherd_, Apr 10 2017

%Y Cf. A019827 (sine of 18 degrees), A019881 (sine of 72 degrees), A001622 (golden ratio phi). A182007.

%K nonn,cons,easy

%O 0,1

%A _N. J. A. Sloane_.

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Last modified February 18 00:37 EST 2020. Contains 332006 sequences. (Running on oeis4.)