Question

помогите срочно :
упростить
1/cos^2(x)-tg^2(x)*(cos^2(x)+1)

Answer 1

$\frac{1}{cos^{2}x}=tg^{2} x+1$
$tg^{2} x(cos^{2}x +1)=sin^{2} x+tg^{2} x$$tg^{2} x+1-sin^{2} x-tg ^{2} x=1-sin ^{2}x=cos^{2} x$