弦长9941.7,半径4100,求弧长抱歉,错了,半径4700,高4100,弦长如上

弦长L=9941.7,高H=4100,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)
=4100/2+9941.7^2/(8*4100)
=5063.34
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((9941.7/2)/5063.34)
=158.06度
C=PI*R*A/180=PI*5063.34*158.06/180=13968.45