Решите пожалуйста первый номер а и б

Решите задачу:

$1)\quad 1-2sin^2\frac{\pi}{12}=(sin^2\frac{\pi}{12}+cos^2\frac{\pi}{12})-2sin^2\frac{\pi}{12}=cos^2\frac{\pi}{12}-sin^2\frac{\pi}{12}=\\\\=cos(2\cdot \frac{\pi}{12})=cos\frac{\pi}{6}=\frac{\sqrt3}{2}\\\\2)\quad sin\frac{7\pi}{36}\cdot cos\frac{\pi}{18}+cos\frac{7\pi}{36}\cdot sin\frac{\pi}{18}=sin(\frac{7\pi}{36}+\frac{\pi}{18})=\\\\=sin\frac{9\pi}{36}=sin\frac{\pi}{4}=\frac{\sqrt2}{2}\\\\\\Formylu:\quad 1-2sin^2 \alpha =cos2 \alpha \\\\sin \alpha \cdot cos \beta +cos \alpha \cdot sin\beta =sin(\alpha +\beta$