Question

1)cos2π/7•cos4π/7•cos6π/7
2)cos2π/7•cos4π/7+cos2π/7•cos6π/7+cos4π/7•cos6π/7​

Answer 1

Ответ:

1)cos(2π/7) • cos(4π/7) • cos(6π/7) = 1/8

2)cos(2π/7) • cos(4π/7) + cos(2π/7) • cos(6π/7) + cos(4π/7) • cos(6π/7) = -1/2