Вычислите sin 11π/30-sin π/30-cos 8π/15-cos 2π/15.

\[= 2 \cdot \frac{1}{2} \cdot \cos\frac{\pi}{5} - 2 \cdot \frac{1}{2} \cdot \cos\frac{\pi}{5} =\]

\[= \cos\frac{\pi}{5} - \cos\frac{\pi}{5} = 0\]