Question

Косинус^2 альфа - 1/ косинус ^2 альфа

Answer 1

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