

A019827


Decimal expansion of sine of 18 degrees.


11



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

0,1


COMMENTS

Decimal expansion of cosine of 72 degrees.
If the offset is changed to 1, the constant is 3.090169.. = 5/A001622.  Omar E. Pol, Nov 15 2007
Also the imaginary part of i^(1/5).  Stanislav Sykora, Apr 25 2012
One of two roots of 4x^2 + 2x  1 (the other is the sine of 54 degrees times 1).  Alonso del Arte, Apr 25 2015


LINKS

Zak Seidov, Table of n, a(n) for n = 0..999
Wikipedia, Exact trigonometric constants


FORMULA

Equals (sqrt(5)  1)/4.
Equals 1/(1 + sqrt(5)).  Omar E. Pol, Nov 15 2007


EXAMPLE

(sqrt(5)  1)/4 = 0.309016994374947424102293417182819...


MATHEMATICA

RealDigits[Sin[18 Degree], 10, 108][[1]] (* Alonso del Arte, Apr 20 2015 *)


PROG

(PARI) sin(Pi/10) \\ Charles R Greathouse IV, Feb 03 2015
(PARI) polrootsreal(4*x^2 + 2*x  1)[2] \\ Charles R Greathouse IV, Feb 03 2015


CROSSREFS

Cf. A019845 (sine of 36 degrees), A019863 (sine of 54 degrees).
Sequence in context: A167004 A259346 A239798 * A201581 A164597 A167295
Adjacent sequences: A019824 A019825 A019826 * A019828 A019829 A019830


KEYWORD

nonn,cons,easy


AUTHOR

N. J. A. Sloane.


STATUS

approved



