Question

Помогите пожалуйста!

Answer 1

$1)frac{Sin^{2}alpha}{Cosalpha-1 }=frac{1-Cos^{2}alpha}{Cosalpha-1 }=frac{(1-Cosalpha )(1+Cosalpha) }{Cosalpha-1 }=-(1+Cosalpha)\\2)1-Cos^{2}alpha+tg^{2}alpha*Cos^{2}alpha=Sin^{2}alpha+frac{Sin^{2}alpha}{Cos^{2}alpha}*Cos^{2} alpha = Sin^{2}alpha+Sin^{2} alpha=2Sin^{2}alpha$$3)frac{1-Sin^{2}alpha}{1-Cos^{2}alpha}+tgalpha*Ctgalpha=frac{Cos^{2}alpha  }{Sin^{2}alpha}+1=Ctg^{2}alpha+1=frac{1}{Sin^{2}alpha}$