login
A375152
Decimal expansion of the apothem (inradius) of a regular 9-gon with unit side length.
7
1, 3, 7, 3, 7, 3, 8, 7, 0, 9, 7, 2, 7, 3, 1, 1, 1, 3, 9, 3, 8, 0, 8, 3, 2, 0, 1, 3, 2, 4, 8, 8, 3, 6, 3, 5, 8, 8, 7, 5, 9, 3, 6, 2, 9, 9, 5, 8, 5, 4, 1, 2, 9, 1, 0, 7, 5, 2, 6, 3, 6, 5, 0, 1, 2, 5, 9, 9, 4, 9, 1, 2, 6, 9, 4, 0, 7, 9, 6, 5, 9, 2, 1, 7, 0, 3, 0, 2, 1, 2
OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Regular Polygon.
Wikipedia, Apothem.
FORMULA
Equals cot(Pi/9)/2 = A019968/2.
Equals 1/(2*tan(Pi/9)) = 1/(2*A019918).
Equals A375151*cos(Pi/9) = A375151*A019879.
Equals A375151 - A375153.
EXAMPLE
1.3737387097273111393808320132488363588759362995854...
MATHEMATICA
First[RealDigits[Cot[Pi/9]/2, 10, 100]]
CROSSREFS
Cf. A375151 (circumradius), A375153 (sagitta), A256853 (area).
Cf. apothem of other polygons with unit side length: A020769 (triangle), A020761 (square), A375067 (pentagon), A010527 (hexagon), A374971 (heptagon), A174968 (octagon), A179452 (10-gon), A375191 (11-gon), A375193 (12-gon).
Sequence in context: A161973 A010705 A244189 * A200481 A016665 A320831
KEYWORD
nonn,cons,easy
AUTHOR
Paolo Xausa, Aug 01 2024
STATUS
approved