A019907 Decimal expansion of tangent of 9 degrees.

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

Offset

0,2

Comments

Also the decimal expansion of cotangent of 81 degrees. - Mohammad K. Azarian, Jun 30 2013

Links

Ivan Panchenko, Table of n, a(n) for n = 0..1000

Wikipedia, Exact trigonometric constants

Index entries for algebraic numbers, degree 8

Formula

Equals tan(Pi/20) = A019818/A019890. - R. J. Mathar, Aug 29 2025

Smallest positive of the 8 real-valued roots of x^8-44*x^6+166*x^4-44*x^2+1=0. (Others A019925, A019961, A019979). - R. J. Mathar, Aug 31 2025

Equals A019827/(1+A019881). - R. J. Mathar, Sep 06 2025

Example

0.158384440324536293838883092694366411433916216...

Mathematica

RealDigits[Tan[9 Degree], 10, 120][[1]] (* Harvey P. Dale, Aug 23 2020 *)

Crossrefs

Sequence in context: A393433 A097908 A198612 * A248007 A212194 A212162

Adjacent sequences: A019904 A019905 A019906 * A019908 A019909 A019910

Keyword

nonn,cons

Author

N. J. A. Sloane

Status

approved