Question

Преобразуйте выражение sin2x ctg2x + sin2x

Answer 1

$sin2x\cdot ctg2x+sin2x=sin2x\cdot \frac{cos2x}{sin2x}+sin2x=cos2x+sin2x=\\\\=cos2x+cos(\frac{\pi}{2}-2x)=2\cdot cos\frac{2x+\frac{\pi}{2}-2x}{2}\cdot cos\frac{2x-\frac{\pi}{2}+2x}{2}=\\\\=2\cdot cos\frac{\pi}{4}\cot cos(2x-\frac{\pi}{4})=\sqrt2\cdot cos(2x-\frac{\pi}{4})$