已知弦长6.5米,拱高0.6米,求弧长?（请给去详细计算公式）急!

已知弦长L=6.5米,拱高H=0.6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)
=0.6/2+6.5^2/(8*0.6)
=9.102米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((6.5/2)/9.102)
=41.84度
=41.84*PI/180
=0.73024弧度
C=A*R
=0.73024*9.102
=6.647米