已知弦长L=4.5米,弦高H=2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)^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)=2/2+4.5^2/(8*2)=2.2656米A=2*ARC SIN((L/2)/R)=2*ARC SIN((4.5/2)/2....