弦长L=8.5m,弦高H=2.9m,求弧长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*H*R+H^2+L^2/42*H*R=H^2+L^2/4R=H/2+L^2/(8*H)=2.9/2+8.5^2/(8*2.9)=4.564mA=2*ARC SIN((L/2)/R)=2*ARC SIN((8.5/2...