Question

Упростите выражение, 10 класс

Answer 1

$\displaystyle\bf \underbrace{1-Sin^{2}\alpha}_{Cos^{2}\alpha } +\frac{Sin^{2}\alpha }{tg^{2}\alpha } =Cos^{2}\alpha +\frac{Sin^{2} \alpha }{\frac{Sin^{2} \alpha }{Cos^{2} \alpha } } =Cos^{2}\alpha +\frac{Sin^{2}\alpha \cdot Cos^{2} \alpha }{Sin^{2} \alpha } =\\\\\\=Cos^{2} \alpha +Cos^{2} \alpha =2Cos^{2} \alpha$