Question

1-sin^2 альфа +tg^2 альфа *cos^2 альфа

Answer 1

$1-\sin^2\alpha+{\rm tg}^2\alpha\cdot \cos^2\alpha=\cos^2\alpha+\dfrac{\sin^2\alpha}{\cos^2\alpha}\cdot \cos^2\alpha=\cos^2\alpha+\sin^2\alpha=1$