已知弦長L=2.2M,弦高H=0.5M,求弧長C,半徑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)
=0.5/2+2.2^2/(8*0.5)
=1.46M
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((2.2/2)/1.46)
=97.776度
C=PI*R*A/180=PI*1.46*97.776/180=2.492M