弦长L=2.5米, 拱高H=0.2米, 请问弧长C是多少?
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)
=0.2/2+2.5^2/(8*0.2)
=4.00625米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((2.5/2)/4.00625)
=36.36度
=36.36*PI/180
=0.634621弧度
C=R*A=4.00625*0.634621=2.542米