玄长L=660玄高H=30求弓形面积S?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*H*R+H^2+L^2/42*H*R=H^2+L^2/4R=H/2+L^2/(8*H)=30/2+660^2/(8*30)=1830A=2*ARC SIN((L/2)/R)=2*ARC SIN((660/2)/183...