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 A019890 Decimal expansion of sine of 81 degrees. 3
 9, 8, 7, 6, 8, 8, 3, 4, 0, 5, 9, 5, 1, 3, 7, 7, 2, 6, 1, 9, 0, 0, 4, 0, 2, 4, 7, 6, 9, 3, 4, 3, 7, 2, 6, 0, 7, 5, 8, 4, 0, 6, 8, 6, 1, 5, 8, 9, 8, 8, 0, 4, 3, 4, 9, 2, 3, 9, 0, 4, 8, 0, 1, 6, 3, 8, 0, 7, 2, 9, 3, 5, 9, 6, 9, 7, 1, 2, 7, 3, 5, 7, 1, 1, 9, 6, 3, 0, 3, 7, 9, 9, 9, 8, 8, 6, 7, 7, 8 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Also the real part of i^(1/10). - Stanislav Sykora, Apr 25 2012 Equals sin(9*Pi/20). - Wesley Ivan Hurt, Sep 01 2014 An algebraic number of degree 8 and denominator 2. - Charles R Greathouse IV, Aug 27 2017 LINKS Ivan Panchenko, Table of n, a(n) for n = 0..1000 Wikipedia, Exact trigonometric constants FORMULA Equals cos(Pi/20) = sqrt((1+A019881)/2) = sqrt(1-A019818^2) = sqrt(5-sqrt(5))*(sqrt(5)+sqrt(5+2*sqrt(5)))/(4*sqrt(5)). - R. J. Mathar, Jun 18 2006 EXAMPLE 0.98768834059513772619004024769343726075840686158988043492390480163... MAPLE Digits:=100: evalf(sin(9*Pi/20)); # Wesley Ivan Hurt, Sep 01 2014 MATHEMATICA RealDigits[Sin[81 Degree], 10, 120][[1]] (* Harvey P. Dale, Aug 11 2012 *) PROG (PARI) sin(9*Pi/20) \\ Charles R Greathouse IV, Aug 27 2017 CROSSREFS Sequence in context: A090671 A132673 A107927 * A066666 A021905 A200688 Adjacent sequences:  A019887 A019888 A019889 * A019891 A019892 A019893 KEYWORD nonn,cons AUTHOR STATUS approved

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Last modified July 20 12:30 EDT 2018. Contains 312804 sequences. (Running on oeis4.)