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A231986 Decimal expansion of the solid angle (in steradians) subtended by a spherical square of one radian side. 8
9, 2, 7, 6, 8, 9, 4, 7, 5, 3, 2, 2, 3, 1, 3, 6, 4, 0, 7, 9, 5, 6, 1, 3, 2, 3, 8, 1, 4, 5, 9, 5, 4, 9, 1, 7, 6, 3, 0, 4, 0, 4, 0, 0, 6, 4, 2, 4, 5, 7, 4, 3, 4, 0, 8, 9, 9, 9, 8, 6, 9, 0, 4, 6, 6, 9, 1, 7, 4, 8, 6, 1, 8, 8, 5, 9, 1, 4, 5, 1, 8, 8, 9, 3, 9, 3, 7, 1, 3, 1, 0, 9, 9, 0, 3, 1, 9, 1, 2, 3, 5, 3, 9, 4, 4 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

In spherical geometry, the solid angle (in steradians) covered by a rectangle with arc-length sides r and s (in radians) equals Omega = 4*arcsin(sin(s/2)*sin(r/2)). For this constant, r = s = 1.

Note: It is a common mistake to think that 1 radian squared gives one steradian! See also the discussion in A231984.

REFERENCES

G. V. Brummelen, Heavenly Mathematics: The Forgotten Art of Spherical Trigonometry, Princeton University Press, 2012, ISBN 978-0691148922.

LINKS

Stanislav Sykora, Table of n, a(n) for n = 0..2000

Wikipedia, Solid angle, Section 3.3 (Pyramid)

Wikipedia, Steradian

FORMULA

4*arcsin(sin(1/2)^2).

EXAMPLE

0.9276894753223136407956132381459549176304040064245743408999869...

CROSSREFS

Cf. A072097 (rad/deg), A019685 (deg/rad), A231981 (sr/deg^2), A231982 (deg^2/sr), A231987 (inverse problem).

Sequence in context: A172423 A104696 A086088 * A203126 A111506 A248316

Adjacent sequences:  A231983 A231984 A231985 * A231987 A231988 A231989

KEYWORD

nonn,cons,easy

AUTHOR

Stanislav Sykora, Nov 17 2013

STATUS

approved

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Last modified August 22 12:54 EDT 2017. Contains 290948 sequences.