知道弦长L=72.177米 弧高H=8.211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)
=8.211/2+72.177^2/(8*8.211)
=83.413米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((72.177/2)/83.413)
=51.27度
=51.27*PI/180
=0.89486弧度
C=A*R
=0.89486*83.413
=74.643米