Question

Срочно 20 балов
1) 1- cos ^2a=?
2) cos a tag a = ?
3) 1/cos^2a - 1=?

Answer 1

$1)1-Cos^{2}\alpha=Sin^{2} \alpha\\\\2)Cos\alpha*tg\alpha=Cos\alpha*\frac{Sin\alpha }{Cos\alpha}=Sin\alpha\\\\3)\frac{1}{Cos^{2}\alpha} -1=\frac{1-Cos^{2}\alpha}{Cos^{2}\alpha}=\frac{Sin^{2}\alpha }{Cos^{2}\alpha}=tg^{2}\alpha$