知道弧高1.2m和玄长3.9m怎么求弧长?
问题描述：
知道弧高1.2m和玄长3.9m怎么求弧长?
答
知道弧高H=1.2m和弦长L=3.9m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)=1.2/2+3.9^2/(8*1.2)=2.1844mA=2*ARC SIN((L/2)/R)=2*ARC SIN((3....