已知cosα=3/5,3π/2

已知cosα=3/5,3π/2
已知cosα=3/5,3π/2

已知cosα=3/5,3π/2
因为3π/2

由cosα=3/5且3π/2<α<2π得
sinα=-√[1-(3/5)²]=-4/5
sin2α=2sinαcosα=-24/25

cosα=3/5,3π/2<α<2π,
sinα=-4/5
求sin2α=2cosαsinα= -24/25