弦長L=3950,弦到弧的距離H=18.5,求弧長C?
弧半徑為R,弧所對的圓心角為A.
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)
=18.5/2+3950^2/(8*18.5)
=105431.547
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((3950/2)/105431.547)
=2.15度
C=π*R*A/180=π*105431.547*2.15/180=3950.231我就是A不會求不客氣！