已知弦长为L=4.5拱高为H=0.7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)^2R^2=R^2-2*R*H+H^2+L^2/42*R*H=H^2+L^2/4R=H/2+L^2/(8*H)=0.7/2+4.5^2/(8*0.7)=3.966A=2*ARC SIN((4.5/2)/3.966)=69.126度=69.1...