弦长L=1612,弦中心到弧顶H=404,求个弧长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)
=404/2+1612^2/(8*404)
=1006.005
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((1612/2)/1006.005)
=106.49度
=106.49*PI/180
=1.858559弧度
C=R*A=1006.005*1.858559=1869.72