cp's OEIS Frontend

A231981 Decimal expansion of one steradian (sr) expressed in square degrees.

%I A231981 #21 Aug 21 2023 12:48:40
%S A231981 3,2,8,2,8,0,6,3,5,0,0,1,1,7,4,3,7,9,4,7,8,1,6,9,4,6,0,7,9,9,5,1,7,5,
%T A231981 5,0,0,5,0,1,2,2,4,2,9,9,3,8,0,7,8,8,1,8,2,5,9,7,7,3,2,6,3,3,3,7,1,2,
%U A231981 0,9,1,1,9,1,7,6,4,2,8,2,9,4,5,9,5,1,8,0,4,7,5,1,9,0,1,4,7,5,3,8,6,8,1,3,6
%N A231981 Decimal expansion of one steradian (sr) expressed in square degrees.
%C A231981 This is the conversion ratio between two solid-angle measures: steradians and square degrees, applicable to integration infinitesimals. The square degree must not be confused with a finite spherical square having one degree side (see A231983, A231984, A231985), just as one steradian must not be confused with the solid angle covered by a spherical square with a side arc-length of one radian (see A231986, A231987).
%C A231981 Equals also full solid angle expressed in degrees, divided by 4*Pi (i.e., A125560/(4*Pi)).
%D A231981 G. V. Brummelen, Heavenly Mathematics: The Forgotten Art of Spherical Trigonometry, Princeton University Press, 2012, ISBN 978-0691148922.
%H A231981 Stanislav Sykora, <a href="/A231981/b231981.txt">Table of n, a(n) for n = 4..2000</a>
%H A231981 Wikipedia, <a href="http://en.wikipedia.org/wiki/Steradian">Steradian</a>
%H A231981 Wikipedia, <a href="http://en.wikipedia.org/wiki/Square_degree">Square degree</a>
%H A231981 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A231981 (180/Pi)^2.
%e A231981 3282.80635001174379478169460799517550050122429938078818259773...
%t A231981 RealDigits[(180/Pi)^2,10,120][[1]] (* _Harvey P. Dale_, Nov 23 2019 *)
%Y A231981 Cf. A000796 (Pi), A125560 (full solid angle), A072097 (rad/deg), A019685 (deg/rad), A231982 (inverse, deg^2/sr), A231983 (square with 1 deg side, in sr), A231984 (square with 1 deg side, in square degrees), A231985, A231986 (square with 1 rad side, in sr), A231987.
%K A231981 nonn,cons,easy
%O A231981 4,1
%A A231981 _Stanislav Sykora_, Nov 16 2013