A256854 Decimal expansion of area of a regular 11-gon with unit edge length.

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

Offset: 1

Author

Stanislav Sykora, Apr 12 2015

Keywords

• nonn
• cons

Examples

			9.36563990694543752488235845328433428788257496183502738768931...
		

Links

• Stanislav Sykora, Table of n, a(n) for n = 1..2000
• Wikipedia, Hendecagon
• Wikipedia, Regular polygon
• Index entries for algebraic numbers, degree 10

Crossrefs

Cf. A000796, A120011 (p=3), A102771 (p=5), A104956 (p=6), A178817 (p=7), A090488 (p=8), A256853 (p=9), A178816 (p=10), A178809 (p=12).

Programs

Mathematica

RealDigits[11/4 Cot[Pi/11],10,120][[1]] (* Harvey P. Dale, Apr 03 2016 *)

PARI

p=11; a=(p/4)*cotan(Pi/p)        \\ Use realprecision in excess

Formula

Equals (p/4)*cot(Pi/p), with p = 11.