Вычислите (cos π/12-sin π/12)(cos π/12+sin π/12).

\[= \cos^{2}\frac{\pi}{12} - \sin^{2}\frac{\pi}{12} =\]

\[= \cos\left( 2 \cdot \frac{\pi}{12} \right) = \cos\frac{\pi}{6} = \frac{\sqrt{3}}{2}\]