弦长L=12.25米弦高H=2米求弧长C?
弧半径为R,弧所对的圆心角为A.
R^2=(R-H)^2+(L/2)^2
R^2=R^2-2*R*H+H^2+L^2/4
2*R*H=H^2+L^2/4
R=H/2+L^2/(8*H)
=2/2+12.25^2/(8*2)
=10.3789米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((12.25/2)/10.3789)
=72.334度
C=π*R*A/180=π*10.3789*72.334/180=13.103米