A019851 - OEIS

A019851

Decimal expansion of sine of 42 degrees.

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

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OFFSET

0,1

COMMENTS

This sequence is also decimal expansion of cosine of 48 degrees. - Mohammad K. Azarian, Jun 29 2013

A quartic number with denominator 2. - Charles R Greathouse IV, Nov 05 2017

LINKS

Ivan Panchenko, Table of n, a(n) for n = 0..1000

Wikipedia, Exact trigonometric constants

Index entries for algebraic numbers, degree 4

FORMULA

Equals cos(4*Pi/15) = (sqrt(5)-1)*(sqrt(3)*sqrt(5+2*sqrt(5))-1)/8 = 8*A019887^4 -8*A019887^2 + 1 = sqrt(1-A019857^2). - R. J. Mathar, Jun 18 2006