8. (2023春•宁波期中)已知α\alphaα为第三象限角,cosα=−35\cos \alpha =-\frac{3}{5}cosα=−53,则sin2α+cos2α1+cos(2α+π)=(\frac{\sin 2\alpha +co{s^2}\alpha }{1+\cos ({2\alpha +\pi })}=(1+cos(2α+π)sin2α+cos2α=( )))