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

[latex]\frac{1}{cos^2\alpha}-cos^2\alpha-tg^2\alpha=\frac{1}{cos^2\alpha}-cos^2\alpha-\frac{sin^2\alpha}{cos^2\alpha}=[/latex] [latex]\frac{1}{cos^2\alpha}-cos^2\alpha-\frac{1-cos^2\alpha}{cos^2\alpha}=\frac{1}{cos^2\alpha}-cos^2\alpha-\frac{1}{cos^2\alpha}+\frac{cos^2\alpha}{cos^2\alpha}=[/latex] [latex]1-cos^2\alpha=sin^2\alpha[/latex]