A387445 Decimal expansion of cos(Pi/25).

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

Offset: 0

Author

R. J. Mathar, Aug 29 2025

Keywords

• nonn
• cons
• new

Examples

			0.99211470131447783105...
		

Links

• R. J. Mathar, Reduction formulas of the cosine of integer fractions of pi, (2008) vixra:2210.0026
• Index entries for algebraic numbers, degree 10

Crossrefs

Cf. A019694.

Formula

Equals sin(23*Pi/50).

Largest of the 10 real-valued roots of 1024*x^10 -2560*x^8 +2240*x^6 -32*x^5 -800*x^4 +40*x^3 +100*x^2 -10*x -1 =0.

16*this^5 -20*this^3 +5*this = A019863.