Объясните, пожалуйста. 1-2

Решите задачу:

$\frac{4cos(3\pi - \beta )-sin(\frac{3\pi}{2}+\beta )}{ 5cos( \beta -\pi )}= \frac{-4cos \beta -(-cos \beta )}{5cos (\pi -\beta )} = \frac{-4cos \beta }{-5cos\beta }=\frac{4}{5}\\\\\\\\ \frac{56}{sin(-\frac{27\pi }{4})cos(\frac{27\pi}{4})} = \frac{56}{-\frac{1}{2}\cdot sin\frac{2\cdot 27\pi }{4}} =-\frac{112}{sin\frac{27\pi }{2}}=-\frac{112}{sin(12\pi +\pi +\frac{\pi}{2})}=\\\\=-\frac{112}{sin(\pi +\frac{\pi}{2})}=-\frac{112}{sin\frac{3\pi}{2}}=-\frac{112}{-1}=112$