Question

Упростить
1) (sin2a-2sina)/cosa-1
2) cos2x/sinx-cosx
25 баллов

Answer 1

$\frac{sin 2a-2sin a}{cos a-1}=\frac{2 sin a*cos a-2sin a}{cos a -1} =\\=\frac{2 sin a(cos a-1)}{cos a-1}=2 sin a\\\\ \frac{cos 2x}{sin x- cos x} =\frac{cos^{2} x-sin^{2} x }{sin x - cos x}=\\=\frac{-(sin x -cos x)(sin x+ cosx)}{sin x- cos x}=-sin x- cos x$