弦长L=12米,拱高H=1.3米,求 弧长C?弧半径为R,弧所对的圆心角为A.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)=1.3/2+12^2/(8*1.3)=14.4962米A=2*ARC SIN((L/2)/R)=2*ARC SIN((12/2)/14.4962)=48.9度C=...