已知弦长4.4求弧长

已知弦长L=4.5弓高H=1.4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)
=1.4/2+4.5^2/(8*1.4)
=2.508
A=2*ARC SIN((L/2)/R
=2*ARC SIN((4.5/2)/2.508
=127.56度
=127.56*PI/180
=2.226397弧度
C=R*A=2.508*2.226397=5.584