算圆形(r-1.35)^2+(10.22/2)^2=r^2-2.7r+1.8225+26.1121=02.7r=27.9346r=10.346弧长对的圆心角a=2*arcsin(5.11/10.346)=60°弧长=La=10.346*兀/3=3.45兀=1.83值是近似的。
