Question

Упростить
1)1-sin^2a+ctg^2a•sin^2a=

Answer 1

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