A387440 -id:A387440 - cp's OEIS frontend

A387443 Decimal expansion of cos(Pi/22).

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

Offset: 0

R. J. Mathar, Aug 29 2025

			0.98982144188093273238...

Index entries for algebraic numbers, degree 10

Cf. A019689.

Equals sin(5*Pi/11) = sqrt( (A387440+1)/2 ).

Largest of the 10 real-valued roots of 1024*x^10 -2816*x^8 +2816*x^6 -1232*x^4 +220*x^2 -11 =0.

A387450 Decimal expansion of cos(Pi/33).

Original entry on oeis.org

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

Offset: 0

R. J. Mathar, Aug 29 2025

			0.99547192257308460473...

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

Equals sin(31*Pi/66) = 2F1(-1/22,1/22;1/2;3/4).
Largest of the 10 real-valued roots  of 1024*x^10 +512*x^9 -2560*x^8 -1280*x^7 +2176*x^6 +1088*x^5 -688*x^4 -344*x^3 +48*x^2 +24*x +1 =0.
4*this^3 -3*this = A387440.

cp's OEIS Frontend

A387443 Decimal expansion of cos(Pi/22).

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