a)
sin 30° = 1/2
cos 60° = 1/2
cos 120° = -1/2
sin 135° = -√2/2
cos 90° = 0

Вычисляем:
а) sin 30° - cos 60° - cos² 120° + sin 135° × cos 90°
= 1/2 - 1/2 - (-1/2) + (-√2/2) × 0
= 1/2 - 1/2 + 1/2
= 0

б)
tg 30° = √3
tg 60° = √3
tg 135° = -1
cos 150° = -√3/2

Вычисляем:
б) tg 30° × tg 60° - tg² 135° + cos 150°
= √3 × √3 - (-1)² + (-√3/2)
= 3 - 1 + (-√3/2)
= 2 - √3/2