23. （2023春•辽宁月考）若cos(7π2+α)=47\cos ({\frac{7\pi }{2}+\alpha })=\frac{4}{7}cos(27π+α)=74，tanα<0\tan \alpha <0tanα<0，cos(π−α)+sin(π2−α)⋅tanα=(\cos ({\pi -\alpha })+\sin ({\frac{\pi }{2}-\alpha })\cdot \tan \alpha =(cos(π−α)+sin(2π−α)⋅tanα=( )))