A375190 - OEIS

%I #16 Feb 05 2025 10:13:55

%S 1,7,7,4,7,3,2,7,6,6,4,4,2,1,1,1,6,6,2,8,5,6,8,3,1,9,6,1,1,6,8,9,7,5,

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

%U 0,0,4,9,5,8,2,6,1,6,6,9,5,0,0,1,7,7,9,5,9,9

%N Decimal expansion of the circumradius of a regular 11-gon with unit side length.

%H Paolo Xausa, <a href="/A375190/b375190.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RegularPolygon.html">Regular Polygon</a>.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Regular_polygon">Regular polygon</a>.

%H <a href="/index/Al#algebraic_10">Index entries for algebraic numbers, degree 10</a>.

%F Equals csc(Pi/11)/2.

%F Equals 1/(2*sin(Pi/11)) = 1/A272489.

%F Equals A375191/cos(Pi/11).

%F Equals A375191 + A375192.

%e 1.774732766442111662856831961168975846105376382123...

%t First[RealDigits[Csc[Pi/11]/2, 10, 100]]

%o (PARI) .5/sin(Pi/11) \\ _Charles R Greathouse IV_, Feb 05 2025

%Y Cf. A375191 (apothem), A375192 (sagitta), A256854 (area).

%Y Cf. circumradius of other polygons with unit side length: A020760 (triangle), A010503 (square), A300074 (pentagon), A374957 (heptagon), A285871 (octagon), A375151 (9-gon), A001622 (10-gon), A188887 (12-gon).

%Y Cf. A272489.

%K nonn,cons,easy,changed

%O 1,2

%A _Paolo Xausa_, Aug 04 2024