1.sinα=m/n cosα=k/n
2.cosα=1/2 sinα=√3/2
cosβ=-1/2 sinβ=√3/2
cosj=-1/2 sinj=-√3/2
cosФ=1/2 sinФ=-√3/2
3.sinα=1 α=π/2 (90°)
sinα=-√3/2 α=4π/3 и 5π/3 (240° и 300°)
cosα=√2/2 α=π/4 и 7π/4 (45° и 315°)
cosα=-1/2 α=2π/3 и 4π/3 (120° и 240°)
sin²α=1-cos²α sin²α=1-(-4/5)²=9/25
т.к. α∈II четверти sinα>0 sinα=√9/25=3/5