3. Вычислите sin 7π/12 + sin π/12 + cos π/12 - cos 7π/12.

sin 7π/12 + sin π/12 = 2 sin(4π/12) cos(3π/12) = 2 sin(π/3) cos(π/4) = 2 * (√3/2) * (√2/2) = √6/2

cos π/12 - cos 7π/12 = -2 sin(4π/12) sin(-3π/12) = -2 sin(π/3) sin(-π/4) = -2 * (√3/2) * (-√2/2) = √6/2

√6/2 + √6/2 = √6