Question

СРОЧНО!!! 50 баллов!!!!!!! ​

Answer 1

$\displaystyle\bf\\\frac{tg^{2} \alpha }{1+tg^{2}\alpha} \cdot\frac{1+Ctg^{2}\alpha}{Ctg^{2}\alpha}-tg^{2}\alpha = \frac{tg^{2} \alpha }{1+tg^{2} \alpha } \cdot\frac{1+\frac{1}{tg^{2} \alpha } }{\frac{1}{tg^{2} \alpha } } -tg^{2} \alpha =\\\\\\=\frac{tg^{2} \alpha }{1+tg^{2} \alpha } \cdot\frac{\frac{1+tg^{2}\alpha }{tg^{2} \alpha } }{\frac{1}{tg^{2}\alpha } } -tg^{2}\alpha=\frac{tg^{2} \alpha }{1+tg^{2}\alpha }\cdot(1+tg^{2} \alpha )-tg^{2} \alpha =\\\\\\=tg^{2} \alpha -tg^{2} \alpha=0$