弦长L=50米弦高H=12米求弧长C、半径R、角度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)=12/2+50^2/(8*12)=32.042米A=2*ARC SIN((L/2)/R)=2*ARC SIN((50/2)/32.042)=102.564度=102....