请问弦长为L=0.9米.弓高为H=0.3米.求弧长C是多少?
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)
=0.3/2+0.9^2/(8*0.3)
=0.4875米
A=2*ARC SIN((L/2)/R)
=2*ARC SIN((0.9/2)/0.4875)
=134.76度
=134.76*PI/180
=2.35201弧度
C=A*R=2.35201*0.4875=1.1466米