弦长L=6.3米.拱高H=0.3米.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)=0.3/2+6.3^2/(8*0.3)=16.6875米A=2*ARC SIN((L/2)/R)=2*ARC SIN((6.3/2)...