已知弦长12.5m,9m,求弧长.急.
问题描述：
已知弦长12.5m,9m,求弧长.急.
答
已知弦长L=12.5m,弓高H=2.9m,求弧长C?弧的半径为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)=2.9/2+12.5^2/(8*2.9)=8.185mA=2*ARC SIN((L/2)/R)=2*ARC SIN((12....