The angle that subtends arc A and chord B is by estimation,
=IF(t>0.985,13*(( (0.075)^2 - (0.925-t)^2)^0.5),((196 -
(t+13)^2)^0.5+0.75*(1-t)*COS((PI()/1.2)*t) + ((EXP(1))^(-0.9*(
t^0.3 ))-0.5)-0.07*SIN(2*PI()*t) - 0.12/((t+1)^200)))
where t=B/A
(Excel) which with a few iterations of Newton's Method, leads to a
soltution
accurate and precise to 9 decimal places.
I constructed the inverse of the curve of (B/A) vs. (2/x)sin(x/2) out of
elementary functions to arrive at this approximation.
For an elaboration and to download the Angle Calculator, see
http://mypeoplepc.com/members/jon8338/math/id15.html
