A380794 Decimal expansion of the obtuse vertex angle, in radians, in a triakis icosahedron face.

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

Offset: 1

Author

Paolo Xausa, Feb 04 2025

Keywords

• nonn
• cons
• easy

Comments

A triakis icosahedron face is an isoscele triangle with two acute angles (A380793) and one obtuse angle (this constant).

Examples

			2.077628612105861047184226260694853007668786641...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Triakis Icosahedron.
• Wikipedia, Triakis icosahedron.

Crossrefs

Cf. A001622, A378973, A378974, A378976, A378977, A380793.

Programs

Mathematica

First[RealDigits[ArcCos[-3*GoldenRatio/10], 10, 100]]

Formula

Equals arccos(-3*A001622/10).

Equals Pi - 2*A380793.