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%I #15 Jul 18 2020 11:41:01
%S 5,5,1,2,8,5,5,9,8,4,3,2,5,3,0,8,0,7,9,4,2,1,4,4,1,5,1,4,6,4,4,5,9,2,
%T 4,2,9,3,3,8,5,0,6,2,8,6,9,0,1,7,8,6,9,6,1,9,1,7,0,0,4,0,8,6,8,4,1,6,
%U 0,5,3,7,1,4,8,5,5,9,2,6,4,9,3,1,7,2,0,0,3,5,1,7,0,4,6,5,6,9,5,4,3,4,6,8,4,7,5
%N Decimal expansion of the steradian solid angle subtended by one triangular facet of the cuboctahedron.
%C Also the vertex solid angle of a regular tetrahedron.
%H Stanislav Sykora, <a href="/A236555/b236555.txt">Table of n, a(n) for n = 0..2000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Cuboctahedron.html">Cuboctahedron</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SphericalPolygon.html">Spherical Polygon</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Platonic_solid">Platonic solid</a>
%F arccos(23/27).
%F 3*arcsin(2*sqrt(2)/3) - Pi. - _Bradley Klee_, Oct 04 2018
%F 8*A236555 + 6*A236556 = 4*Pi. - _Bradley Klee_, Oct 04 2018
%e 0.55128559843253080794214415146445924293385062869017869619170040868416...
%t RealDigits[N[ArcCos[23/27], 107]][[1]] (* _T. D. Noe_, Jan 29 2014 *)
%Y Cf. A236556. Icosidodecahedron: A319881, A319883. Vertex Angles: A019669, A236557, A236558.
%K nonn,cons,easy
%O 0,1
%A _Stanislav Sykora_, Jan 28 2014
%E Definition corrected by _Bradley Klee_, Oct 04 2018
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