Вычислите 2sin 7π/12 cos 7π/12.

\[2\sin\frac{7\pi}{12}\cos\frac{7\pi}{12} = \sin\left( 2 \cdot \frac{7\pi}{12} \right) =\]

\[= \sin\frac{7\pi}{6} = \sin\left( \pi + \frac{\pi}{6} \right) =\]

\[= - \sin\frac{\pi}{6} = - \frac{1}{2}\]