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A073052 Decimal expansion of cos(Pi/7).

%I A073052 #14 Feb 05 2025 11:42:58
%S A073052 9,0,0,9,6,8,8,6,7,9,0,2,4,1,9,1,2,6,2,3,6,1,0,2,3,1,9,5,0,7,4,4,5,0,
%T A073052 5,1,1,6,5,9,1,9,1,6,2,1,3,1,8,5,7,1,5,0,0,5,3,5,6,2,4,2,3,1,9,9,4,3,
%U A073052 2,4,2,0,4,2,7,9,3,9,9,6,5,5,0,1,3,6,1,4,5,4,7,1,8,5,1,2,4,1,5,3,1,8,3,1,0
%N A073052 Decimal expansion of cos(Pi/7).
%C A073052 Cubic number with denominator 2 and minimal polynomial 8*x^3 - 4*x^2 - 4*x + 1. - _Charles R Greathouse IV_, May 13 2019
%H A073052 G. C. Greubel, <a href="/A073052/b073052.txt">Table of n, a(n) for n = 0..10000</a>
%H A073052 Kevin S. Brown's MathPages, <a href="http://www.mathpages.com/home/kmath186.htm">Radical Expression For cos(2*Pi/7)</a>
%H A073052 <a href="/index/Al#algebraic_03">Index entries for algebraic numbers, degree 3</a>.
%F A073052 Equals Hypergeometric2F1([5/7, 2/7], [1/2], 3/4)/2 . - _R. J. Mathar_, Oct 27 2008
%F A073052 Equals (1/6)*(1 + (7*(-1 +3*sqrt(3)*I)/2)^(1/3) + (-7*(1 +3*sqrt(3)*I)/2)^(1/3)). - _G. C. Greubel_, Sep 04 2022
%e A073052 Cos(Pi/7) = 0.90096886790241912623610231950744505116139...
%t A073052 RealDigits[ Cos[Pi/7], 10, 105] [[1]]
%o A073052 (PARI) cos(Pi/7) \\ _Charles R Greathouse IV_, May 13 2019
%o A073052 (Magma) R:= RealField(120); Cos(Pi(R)/7); // _G. C. Greubel_, Sep 04 2022
%o A073052 (SageMath) numerical_approx(cos(pi/7), digits=120) # _G. C. Greubel_, Sep 04 2022
%Y A073052 Cf. A232736 (cos(3*Pi/7)).
%K A073052 cons,nonn
%O A073052 0,1
%A A073052 _Robert G. Wilson v_, Aug 15 2002