弦长L=2.4米 拱高H=0.6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)
=0.6/2+2.4^2/(8*0.6)
=1.5米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((2.4/2)/1.5)
=106.26度
=106.26*PI/180
=1.85459弧度
C=R*A=1.5*1.85459=2.782米