A195698 Decimal expansion of arccos(-sqrt(1/3)).

2, 1, 8, 6, 2, 7, 6, 0, 3, 5, 4, 6, 5, 2, 8, 3, 9, 6, 0, 2, 9, 8, 7, 8, 6, 2, 8, 0, 7, 6, 3, 7, 4, 5, 1, 2, 9, 9, 5, 3, 7, 5, 4, 7, 0, 4, 3, 6, 5, 1, 0, 0, 3, 3, 0, 0, 1, 5, 2, 4, 6, 4, 6, 2, 9, 8, 5, 9, 0, 4, 3, 6, 0, 3, 8, 2, 2, 3, 2, 5, 4, 3, 2, 4, 0, 6, 4, 3, 2, 2, 2, 7, 5, 6, 4, 8, 8, 9, 9, 4

Offset: 1

Author

Clark Kimberling, Sep 23 2011

Keywords

• nonn
• cons

Comments

Dihedral angle between mixed type faces of the truncated octahedron. - R. J. Mathar, Mar 24 2012

Examples

			arccos(-1/sqrt(3)) = 2.1862760354...
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000
• Wikipedia, Truncated Octahedron.
• Index entries for transcendental numbers

Crossrefs

Cf. A195695.

Programs

Magma

[Arccos(-1/Sqrt(3))]; // G. C. Greubel, Nov 18 2017

Mathematica

(See A195695.)
RealDigits[ArcCos[-1/Sqrt[3]], 10, 50][[1]] (* G. C. Greubel, Nov 18 2017 *)

PARI

acos(-1/sqrt(3)) \\ G. C. Greubel, Nov 18 2017

Formula

Equals Pi - arcsin(sqrt(2/3)) = Pi - arctan(sqrt(2)). - Amiram Eldar, Jul 08 2023