|
%I #12 Aug 21 2023 11:38:07
%S 8,1,2,2,9,9,2,4,0,5,8,2,2,6,5,8,1,5,3,8,9,6,7,8,5,3,0,5,3,7,8,3,6,1,
%T 6,2,3,8,7,2,5,8,6,7,8,8,0,3,6,8,7,7,5,0,7,6,9,5,1,1,7,9,7,8,4,1,6,8,
%U 2,2,5,2,4,0,1,8,6,2,3,7,0,8,0,6,7,1,9,3,3,8,6,1,7,4,1,2,6,2,6,2,0,4,2,5,9
%N Decimal expansion of 5/(2*sqrt(5+2*sqrt(5))), area of regular pentagram with base edge length 1.
%C An algebraic number of degree 4: the smaller positive root of 16x^4 - 200x^2 + 125. - _Charles R Greathouse IV_, Dec 03 2012
%H Thomas M. Green, <a href="http://www.contracosta.edu/legacycontent/math/stararea.htm">Area of Pentagram</a>
%H <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>
%e 0.81229924058226581538967853053783616238725867880368775076951179784168...
%t a=1;area=5/(2*Sqrt[5+2*Sqrt[5]]);RealDigits[N[area,20]]
%o (PARI) 5/sqrt(20+8*sqrt(5)) \\ _Charles R Greathouse IV_, Dec 03 2012
%Y Cf. A002194, A010502, A102771, A120011, A179047, A179048, A104956.
%K nonn,cons,easy
%O 0,1
%A _Vladimir Joseph Stephan Orlovsky_, Jun 26 2010
%E Offset corrected, keyword:cons inserted by _R. J. Mathar_, Jun 28 2010
%E Name corrected by _Charles R Greathouse IV_, Dec 03 2012
|
