Question

Упростите выражение: $\frac{1-2sin^2 \alpha }{2tg(45°- \alpha )cos^2(45°- \alpha )}$

Answer 1

$\frac{cos2\alpha}{2\frac{sin(45-\alpha)}{cos(45-\alpha)}*cos(45-\alpha)}=\frac{cos2\alpha}{2sin(45-\alpha)*cos(45-\alpha)}=\frac{cos2\alpha}{sin(90-2\alpha)}=\frac{cos2\alpha}{cos2\alpha}=1$