A375191 Decimal expansion of the apothem (inradius) of a regular 11-gon with unit side length.

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

Offset: 1

Author

Paolo Xausa, Aug 04 2024

Keywords

• nonn
• cons
• easy

Examples

			1.702843619444625004524065173324424415978649993...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Regular Polygon.
• Wikipedia, Apothem.
• Index entries for algebraic numbers, degree 10.

Crossrefs

Cf. A375190 (circumradius), A375192 (sagitta), A256854 (area).

Cf. apothem of other polygons with unit side length: A020769 (triangle), A020761 (square), A375067 (pentagon), A010527 (hexagon), A374971 (heptagon), A174968 (octagon), A375152 (9-gon), A179452 (10-gon), A375193 (12-gon).

Programs

Mathematica

First[RealDigits[Cot[Pi/11]/2, 10, 100]]

PARI

 5/tan(Pi/11) \\ Charles R Greathouse IV, Feb 05 2025

Formula

Equals cot(Pi/11)/2.

Equals 1/(2*tan(Pi/11)).

Equals A375190*cos(Pi/11).

Equals A375190 - A375192.