A019940 - OEIS

%I #17 Sep 08 2022 08:44:44

%S 9,0,0,4,0,4,0,4,4,2,9,7,8,3,9,9,4,5,1,2,0,4,7,7,2,0,3,8,8,5,3,7,1,7,

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

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

%N Decimal expansion of tangent of 42 degrees.

%C Also the decimal expansion of cotangent of 48 degrees. - _Ivan Panchenko_, Sep 01 2014

%H Ivan Panchenko, <a href="/A019940/b019940.txt">Table of n, a(n) for n = 0..1000</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Exact_trigonometric_constants">Exact trigonometric constants</a>

%F Equals sqrt(7 + 2*sqrt(5) - 2*sqrt(3*(5 + 2*sqrt(5)))). - _G. C. Greubel_, Nov 25 2018

%e 0.900404044297839945120477203885371702076466211299485282427079...

%t RealDigits[Tan[42 Degree],10,120][[1]] (* _Harvey P. Dale_, Sep 05 2012 *)

%t RealDigits[Tan[7*Pi/30], 10, 100][[1]] (* _G. C. Greubel_, Nov 25 2018 *)

%o (PARI) default(realprecision, 100); tan(7*Pi/30) \\ _G. C. Greubel_, Nov 25 2018

%o (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Tan(7*Pi(R)/30); // _G. C. Greubel_, Nov 25 2018

%o (Sage) numerical_approx(tan(7*pi/30), digits=100) # _G. C. Greubel_, Nov 25 2018

%Y Cf. A019851 (sine of 42 degrees)

%K nonn,cons

%O 0,1

%A _N. J. A. Sloane_