弦长L=23米,弦中心到弧顶H=1米5,求个弧长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)
=1.5/2+23^2/(8*1.5)
=44.833米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((23/2)/44.833)
=29.726度
=29.726*PI/180
=0.51881弧度
C=A*R=0.51881*44.833=23.26米