Question

1 деленное на cos^2 альфа минус cos^2 альфа минус tg^2 альфа

Answer 1

$frac{1}{cos^2alpha}-cos^2alpha-tg^2alpha=frac{1}{cos^2alpha}-cos^2alpha-frac{sin^2alpha}{cos^2alpha}=$

$frac{1}{cos^2alpha}-cos^2alpha-frac{1-cos^2alpha}{cos^2alpha}=frac{1}{cos^2alpha}-cos^2alpha-frac{1}{cos^2alpha}+frac{cos^2alpha}{cos^2alpha}=$

$1-cos^2alpha=sin^2alpha$