Question

Cos2a+sin^2a=(1-sin a)(1+sin a) докажите тожденство

Answer 1

$\cos2 \alpha +\sin^2 \alpha =1-2\sin^2 \alpha +\sin^2 \alpha =1-\sin^2 \alpha =\\ \\ \\ =\boxed{(1-\sin \alpha )(1+\sin \alpha )}$