Преобразовать в произведение sin2Пи\5+sinПи\5

Question

Преобразовать в произведение sin2Пи\5+sinПи\5

Answer 1

Sin(2π/5)+sin(π/5)=2sin[(2π/5+π/5)/2]cos[(2π/5-π/5)/2]=
=2sin(3π/10)cos(π/10)