圆弧弦长L=5.1米,玄高H=80cm,弧长C是多少?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)=0.8/2+5.1^2/(8*0.8)=4.464米A=2*ARC SIN((L/2)/R)=2*ARC SIN((5...