sin (3π + α) tg (π + α) 28) ctg (2π – α) sin (π + α) 2

28)

$$\frac{sin(\frac{3\pi}{2} + \alpha) \cdot tg(\frac{\pi}{2} + \alpha)}{ctg(2\pi - \alpha) \cdot sin(\pi + \alpha)} =$$ $$\frac{-cos \alpha \cdot (-ctg \alpha)}{-ctg \alpha \cdot (-sin \alpha)} = $$ $$\frac{cos \alpha}{sin \alpha} = ctg \alpha$$

sin (3π/2 + α) = -cos α

tg (π/2 + α) = -ctg α

ctg (2π – α) = -ctg α

sin (π + α) = -sin α

Ответ: ctg α