弧高H=0.8,弦长L=3.020,求弧长C?
弧半径为R,弧所对的圆心角为A.
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)
=0.8/2+3.02^2/(8*0.8)
=1.825
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((3.02/2)/1.825)
=111.659度
C=π*R*A/180=π*1.825*111.659/180=3.5567