A019946 - OEIS

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A019946

Decimal expansion of tangent of 48 degrees.

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

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OFFSET

1,5

COMMENTS

Also the decimal expansion of cotangent of 42 degrees. - Ivan Panchenko, Sep 01 2014

LINKS

Ivan Panchenko, Table of n, a(n) for n = 1..1000

Wikipedia, Exact trigonometric constants

FORMULA

Equals cot(7*Pi/30) = sqrt(23 - 10*sqrt(5) + 2*sqrt(3*(85 -38*sqrt(5)))). - G. C. Greubel, Nov 24 2018

Let r(n) = (n - 1)/(n + 1) if n mod 4 = 1, (n + 1)/(n - 1) otherwise; then this constant equals with Product_{n>=0} r(30*n+15) = (8/7) * (22/23) * (38/37) * (52/53) ... - Dimitris Valianatos, Sep 14 2019

EXAMPLE

1.11061251482919287014348196416513553257695951039085904818440222...

MATHEMATICA

RealDigits[Tan[48 Degree], 10, 120][[1]] (* Harvey P. Dale, Nov 26 2011 *)

RealDigits[Tan[4*Pi/15], 10, 100][[1]] (* G. C. Greubel, Nov 24 2018 *)

PROG

(PARI) default(realprecision, 100); tan(4*Pi/15) \\ G. C. Greubel, Nov 24 2018

(Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Tan(4*Pi(R)/15); // G. C. Greubel, Nov 24 2018

(Sage) numerical_approx(tan(4*pi/15), digits=100) # G. C. Greubel, Nov 24 2018

CROSSREFS

Cf. A019857 (sine of 48 degrees).

Sequence in context: A083463 A187110 A013672 * A090551 A220782 A274617

Adjacent sequences: A019943 A019944 A019945 * A019947 A019948 A019949

KEYWORD

nonn,cons

AUTHOR

N. J. A. Sloane

STATUS

approved