A019860 -id:A019860 - cp's OEIS frontend

A019887 Decimal expansion of sine of 78 degrees.

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

Offset: 0

N. J. A. Sloane

Equals sin(13*Pi/30). - Wesley Ivan Hurt, Aug 31 2014

A quartic number with denominator 2 and minimal polynomial 16x^4 + 8x^3 - 16x^2 - 8x + 1. - Charles R Greathouse IV, Aug 27 2017

			0.9781476007338056379285667478695995324597378088626771078851...

Ivan Panchenko, Table of n, a(n) for n = 0..1000
Wikipedia, Exact trigonometric constants
Index entries for algebraic numbers, degree 4

Digits:=100: evalf(sin(13*Pi/30)); # Wesley Ivan Hurt, Aug 31 2014

First@RealDigits[Sin[78 Degree], 10, 120] (* Michael De Vlieger, Aug 31 2014 *)

cos(Pi/15) \\ Charles R Greathouse IV, Aug 27 2017

Equals cos(Pi/15) = [sqrt(5)-1]*[1+sqrt(3)*sqrt{5+2*sqrt(5)}]/8 = [A002163-1]*[1+A002194*A019970]/8. - R. J. Mathar, Jun 18 2006
Equals 2*A019848*A019860. - R. J. Mathar, Jan 17 2021
4*this^3 -3*this = A019863. - R. J. Mathar, Aug 29 2025
Equals 2F1(-1/10,1/10 ; 1/2 ; 3/4). - R. J. Mathar, Aug 31 2025
A root of 16*x^4+8*x^3-16*x^2-8*x+1=0. - R. J. Mathar, Aug 31 2025

A019949 Decimal expansion of tangent of 51 degrees.

Original entry on oeis.org

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

Offset: 1

N. J. A. Sloane

Also the decimal expansion of cotangent of 39 degrees. - Ivan Panchenko, Sep 01 2014

			1.2348971565350513985561746953759351400536255840779765364212592...

Ivan Panchenko, Table of n, a(n) for n = 1..1000
Wikipedia, Exact trigonometric constants

Cf. A019860 (sine of 51 degrees).

SetDefaultRealField(RealField(100)); R:= RealField(); Tan(17*Pi(R)/60); // G. C. Greubel, Nov 23 2018

RealDigits[Tan[17*Pi/60], 10, 100][[1]] (* G. C. Greubel, Nov 23 2018 *)
RealDigits[Tan[51 Degree],10,120][[1]] (* Harvey P. Dale, Jan 18 2021 *)

default(realprecision, 100); tan(17*Pi/60) \\ G. C. Greubel, Nov 23 2018

numerical_approx(tan(17*pi/60), digits=100) # G. C. Greubel, Nov 23 2018

Equals cot(13*Pi/60) = ((2+sqrt(3))*(3-sqrt(5)) -2)*(2 + sqrt(2*(5 + sqrt(5))))/4. - G. C. Greubel, Nov 23 2018

cp's OEIS Frontend

A019887 Decimal expansion of sine of 78 degrees.

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