跨度L=5米,拱高H=1米,弧长C多长米? 弧半径为R，弧所对的圆心角为A。R=H/2+L^2/(8*H)=1/2+5^2/(8*1)=3.625米A=2*ARC COS((R-H)/R)=2*ARC COS((3.625-1)/3.625)=87.206度C=π*R*A/180=π*3.625*87.206/180=5.5173米
