tolong kerjakan nomor 20

= {2 cos (105+15 / 2) . sin (105-15 / 2)} / {-2 sin (105+15 / 2) . sin (105-15 / 2)}
= {2 cos 60 . sin 45} / {-2 sin 60 . sin 45}
= - cos 60 / sin 60
= - cot 60
= -⅓√3