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%I #15 Mar 01 2023 15:34:26
%S 7,0,5,2,8,7,7,9,3,6,5,5,0,9,3,0,8,6,3,0,7,5,4,0,0,0,6,6,0,0,3,7,5,6,
%T 4,0,3,6,9,9,3,1,5,6,8,9,9,0,9,2,0,5,1,7,1,1,8,2,8,8,9,3,6,4,3,9,6,0,
%U 2,5,3,5,6,1,9,3,9,6,0,4,4,3,6,6,3,8,1,2,8,7,1,1,6,3,9,4,1,2,3,5,4,3,1,4,8
%N Decimal expansion of 180*arccos(1/3)/Pi.
%C Dihedral angle in degrees of regular tetrahedron.
%C Polar angle (or apex angle) of the cone that subtends exactly one third of the full solid angle. - _Stanislav Sykora_, Feb 20 2014
%H G. C. Greubel, <a href="/A137915/b137915.txt">Table of n, a(n) for n = 2..10001</a>
%H Frank Jackson and Eric W. Weisstein, <a href="http://mathworld.wolfram.com/Tetrahedron.html">Tetrahedron</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DihedralAngle.html">Dihedral Angle</a>
%F 180*A137914/Pi = 180*arccos(1/3)/Pi.
%e 70.52877936550930863075400066003756403699315689909205171182889364396025356...
%t RealDigits[180 ArcCos[1/3]/Pi,10,120][[1]] (* _Harvey P. Dale_, Jul 13 2013 *)
%o (PARI) 180*acos(1/3)/Pi
%o (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); 180*Arccos(1/3)/Pi(R); // _G. C. Greubel_, Aug 20 2018
%Y Cf. A137914 (same in radians).
%K cons,nonn
%O 2,1
%A _Rick L. Shepherd_, Feb 22 2008