Cos п/12 - cos 5п/12

Question

Cos п/12 - cos 5п/12

Answer 1

Решение
cosπ/12 - cos5π/12 = - 2*sin[(π/12 + 5π/12)/2]*sin[(π/12 - 5π/12)/2] =
=  2*sin(π/4)*sin(π/6) = 2*(√2/2)*(1/2) = √2/2