宽L=1470高H=600 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)=600/2+1470^2/(8*600)=750.1875A=2*ARC SIN((L/2)/R)=2*ARC SIN((1470/2)/750.1875)=156.9度C=π*R*A/180=π*750.1875*156.9/180=2054.365