弦长L=10 弦中心到弧顶H=0.4 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)
=0.4/2+10^2/(8*0.4)
=31.45
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((10/2)/31.45)
=18.296度
=18.296*PI/180
=0.31932弧度
C=A*R=0.31932*31.45=10.043