A387441 Decimal expansion of cos(Pi/13).

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

Offset: 0

Author

R. J. Mathar, Aug 29 2025

Keywords

• nonn
• cons
• new

Examples

			0.97094181742605202716...
		

Links

• R. J. Mathar, Reduction formulas of the cosine of integer fractions of pi, (2008) vixra:2210.0026
• Index entries for algebraic numbers, degree 6

Crossrefs

Cf. A019680.

Formula

Largest of the 6 real-valued roots of 64*x^6 -32*x^5 -80*x^4 +32*x^3 +24*x^2 -6*x -1 = 0.

Equals sin(11/26*Pi).