3.(2023•包头二模)已知α∈(−π2,π2)\alpha \in ({-\frac{\pi }{2},\frac{\pi }{2}})α∈(−2π,2π),且8sinα−3cos2α+5=08\sin \alpha -3\cos 2\alpha +5=08sinα−3cos2α+5=0,则sinα=(\sin \alpha =(sinα=( )))