%I #15 Aug 07 2024 08:38:00

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

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

%U 8,1,8,5,7,1,3,5,6,9,9,0,4,7,9,9,1,0,3,4,3,3

%N Decimal expansion of the sagitta of a regular 10-gon with unit side length.

%H Paolo Xausa, <a href="/A375189/b375189.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 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Sagitta.html">Sagitta</a>

%F Equals tan(Pi/20)/2 = A019907/2.

%F Equals (1 + sqrt(5) - sqrt(5 + 2*sqrt(5)))/2.

%F Equals A001622 - A179452.

%e 0.0791922201622681469194415463471832057169581080...

%t First[RealDigits[Tan[Pi/20]/2, 10, 100]]

%Y Cf. A001622 (circumradius), A179452 (apothem), A178816 (area).

%Y Cf. sagitta of other polygons with unit side length: A020769 (triangle), A174968 (square), A375068 (pentagon), A375069 (hexagon), A374972 (heptagon), A375070 (octagon), A256853 (9-gon), A375192 (11-gon), A375194 (12-gon).

%Y Cf. A019907.

%K nonn,cons,easy

%O -1,1

%A _Paolo Xausa_, Aug 04 2024