1. ,tgальфа=2.

Решите задачу:

$1.\; \frac{sin \alpha -cos \alpha }{sin \alpha +cos \alpha }=\frac{\frac{sin \alpha -cos \alpha }{cos \alpha }}{\frac{sin \alpha +cos \alpha }{cos \alpha }}=\frac{tg \alpha -1}{tg \alpha +1}=\frac{\frac{2}{5}-1}{\frac{2}{5}+1}=\frac{2-5}{2+5}=-\frac{3}{7}\\\\2.\; \frac{tg \alpha }{ctg \alpha }+tg \beta \cdot ctg \beta =\frac{tg \alpha }{\frac{1}{tg \alpha }}+1=tg^2 \alpha +1=\frac{1}{cos^2 \alpha }$