A019918 Decimal expansion of tangent of 20 degrees.

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

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• changed

Comments

Also the decimal expansion of cotangent of 70 degrees. - Mohammad K. Azarian, Jun 30 2013

Examples

			0.36397023426620236135104788277683404389047...
		

Links

• Ivan Panchenko, Table of n, a(n) for n = 0..1000
• Index entries for algebraic numbers, degree 6.

Crossrefs

Cf. A019938 (tan(2*Pi/9)).

Programs

Maple

evalf(tan(Pi/9), 100); # Bernard Schott, Apr 19 2022

Mathematica

First[RealDigits[Tan[Pi/9], 10, 100]] (* Paolo Xausa, Aug 01 2024 *)

PARI

tan(Pi/9) \\ Charles R Greathouse IV, Feb 05 2025

PARI

polrootsreal(x^6-33*x^4+27*x^2-3)[4] \\ Charles R Greathouse IV, Feb 05 2025

Formula

Equals tan(Pi/9) = A019829/A019879. - Bernard Schott, Apr 19 2022

Smallest positive of the 6 real roots of x^6-33*x^4+27*x^2-3=0. (Other A019978, A019938). - R. J. Mathar, Aug 31 2025