题目内容：

知道弦长80,怎么求弧长?

优质解答

知道弦长L=80,弧高H=30,怎么求弧长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)=30/2+80^2/(8*30)=41.67A=2*ARC SIN((L/2)/R)=2*ARC SIN((80/2)/41.67...