A195710 Decimal expansion of arccos(-sqrt(2/5)).

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

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..5000

Formula

Equals Pi - arcsin(sqrt(3/5)) = Pi - arctan(sqrt(3/2)). - Amiram Eldar, Jul 08 2023

Example

arccos(-sqrt(2/5)) = 2.25551552979717...

Mathematica

r = Sqrt[1/5]; s = Sqrt[2/5];
N[ArcSin[r], 100]
RealDigits[%]  (* A073000 *)
N[ArcCos[r], 100]
RealDigits[%]  (* A105199 *)
N[ArcTan[r], 100]
RealDigits[%]  (* A188595 *)
N[ArcCos[-r], 100]
RealDigits[%]  (* A137218 *)
N[ArcSin[s], 100]
RealDigits[%]  (* A195701 *)
N[ArcCos[s], 100]
RealDigits[%]  (* A195708 *)
N[ArcTan[s], 100]
RealDigits[%]  (* A195709 *)
N[ArcCos[-s], 100]
RealDigits[%]  (* A195710 *)
RealDigits[ArcCos[-Sqrt[(2/5)]], 10, 120][[1]] (* Harvey P. Dale, Apr 06 2023 *)

Prog

(PARI) acos(-sqrt(2/5)) \\ G. C. Greubel, Nov 18 2017
(Magma) [Arccos(-Sqrt(2/5))]; // G. C. Greubel, Nov 18 2017

Crossrefs

Cf. A195708, A195701.

Sequence in context: A236935 A213187 A317921 * A321304 A361361 A280511

Adjacent sequences: A195707 A195708 A195709 * A195711 A195712 A195713

Keyword

nonn,cons

Author

Clark Kimberling, Sep 23 2011

Status

approved