已知弦長L=6.5米,拱高H=1米,求弧長C?
弧半徑為R,弧所對的圓心角為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)
=1/2+6.5^2/(8*1)
=5.78125米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((6.5/2)/5.78125)
=68.41度
=68.41*PI/180
=1.193996弧度
C=R*A=5.78125*1.193996=6.903米