Question

Помогите с алгеброй :)
sin π/8×cos π/8=
sin²α×cos²α=
sin² π/8-cos² π/8=
sin π/12×cos π/12=
2tg15°/1-tg²15°=
(1-sin )×(1+sin)=
sin20°/cos10°=
1+cos8α=