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 A231987 Decimal expansion of the side length (in radians) of the spherical square whose solid angle is exactly one steradian. 7
 1, 0, 4, 1, 1, 9, 1, 8, 0, 3, 6, 0, 6, 8, 7, 3, 3, 4, 0, 2, 3, 4, 6, 0, 7, 5, 3, 3, 5, 9, 2, 5, 6, 8, 7, 8, 8, 9, 0, 0, 6, 9, 6, 6, 7, 6, 0, 0, 6, 0, 8, 7, 1, 3, 4, 9, 1, 5, 2, 3, 0, 2, 8, 1, 3, 1, 2, 9, 9, 7, 1, 9, 7, 0, 4, 8, 2, 2, 3, 8, 5, 8, 9, 2, 8, 9, 5, 5, 5, 8, 8, 7, 1, 8, 8, 6, 4, 4, 3, 0, 7, 2, 7, 5, 9 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS This is an inverse problem (but not an inverse value) to the one leading to A231986: what is the side s of a spherical square (in radians, rad) if it covers a given solid angle (in steradians, sr)? The solution (inverse of the formula in A231896) is s = 2*arcsin(sqrt(sin(Omega/4))). In this particular case, Omega = 1. LINKS Stanislav Sykora, Table of n, a(n) for n = 1..2000 Wikipedia, Solid angle, Section 3.3 (Pyramid) Wikipedia, Steradian FORMULA 2*arcsin(sqrt(sin(1/4))). EXAMPLE 1.041191803606873340234607533592568788900696676006087134915230281312997... PROG (PARI) default(realprecision, 120); 2*asin(sqrt(sin(1/4))) \\ or solve(x = 1, 2, 4*asin((sin(x/2))^2) - 1) \\ least positive solution - Rick L. Shepherd, Jan 28 2014 CROSSREFS Cf. A072097 (rad/deg), A019685 (deg/rad), A231981 (sr/deg^2), A231982 (deg^2/sr), A231986 (inverse problem). Sequence in context: A206438 A128137 A232530 * A235214 A208606 A136100 Adjacent sequences:  A231984 A231985 A231986 * A231988 A231989 A231990 KEYWORD nonn,cons,easy AUTHOR Stanislav Sykora, Nov 17 2013 EXTENSIONS Formula and comment corrected by Rick L. Shepherd, Jan 28 2014 STATUS approved

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Last modified November 16 09:21 EST 2018. Contains 317268 sequences. (Running on oeis4.)