已知弦长L=11.6米,弦高H=0.4米求弧长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+11.6^2/(8*0.4)
=42.25米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((11.6/2)/42.25)
=15.78度
=15.78*PI/180
=0.275426弧度
C=R*A=42.25*0.275426=11.637米