弦高H=1米 弦长L=7.2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)
=1/2+7.2^2/(8*1)
=6.98米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((7.2/2)/6.98)
=62.096度
C=π*R*A/180=π*6.98*62.096/180=7.565米