已知弦长50米弦高6.5米求半径和弧长

已知弦长L=50米,弦高H=6.5米,求半径R和弧长C?
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)
=6.5/2+50^2/(8*6.5)
=51.327米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((50/2)/51.327)
=58.3度
=58.3*PI/180
=1.01747弧度
C=A*R
=1.01747*51.327
=52.224米