已知弦长L=8拱高H=1.8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^2/4 2*R*H=H^2+L^2/4 R=H/2+L^2/(8*H)=1.8/2+8^2/(8*1.8)=5.344米A=2*ARC SIN((L/2)/R)=2*ARC SIN((8/2)/5.344)=...