A019968 Decimal expansion of tangent of 70 degrees.

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

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• cons
• changed

Comments

Also the decimal expansion of cotangent of 20 degrees. - Ivan Panchenko, Sep 01 2014

An algebraic number of degree 6 and denominator 3. - Charles R Greathouse IV, Aug 27 2017

Examples

			2.7474774194546222787616640264976727177518725991708258215...
		

Links

• Ivan Panchenko, Table of n, a(n) for n = 1..1000
• Index entries for algebraic numbers, degree 6

Crossrefs

Cf. A019879 (sine of 70 degrees).

Programs

Magma

SetDefaultRealField(RealField(100)); R:= RealField(); Tan(7*Pi(R)/18); // G. C. Greubel, Nov 21 2018

Mathematica

RealDigits[Tan[7*Pi/18], 10, 100][[1]] (* G. C. Greubel, Nov 21 2018 *)

PARI

tan(7*Pi/18) \\ Charles R Greathouse IV, Aug 27 2017

Sage

numerical_approx(tan(7*pi/18), digits=100) # G. C. Greubel, Nov 21 2018

Formula

Equals A019879/A019829. - R. J. Mathar, Aug 29 2025

Largest positive of the 6 real-values roots of 3*x^6 -27*x^4 +33*x^2 -1 =0. (Others: A019948, A019908). - R. J. Mathar, Aug 29 2025