12.(2023春•渭滨区期末)曲线f(x)=lnx−2xf(x)=lnx-\frac{2}{x}f(x)=lnx−x2在x=1x=1x=1处切线的倾斜角为α\alphaα,则cosαsinα−4cosα=(\frac{\cos \alpha }{\sin \alpha -4\cos \alpha }=(sinα−4cosαcosα=( )))