Question

помогите !!!!!!! !!!!!​

Answer 1

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