Cos п/5 + cos 2п/5 + cos 4п/5 + cos 6п/5 - вопрос №36656195254565 от irochka320969 04.10.2022 07:17

Question

Алгебра: Cos п/5 + cos 2п/5 + cos 4п/5 + cos 6п/5

irochka320969 · Answer

Cos(π/5)+cos(2π/5)+cos(4π/5)+cos(6π/5)==cos(π/5+cos(2π/5)+cos(π-(π/5))+cos(π+(π/5)=по формулам приведения=cos(π/5+cos(2π/5)-cos(π/5)-сos(π/5)==cos(2π/5)-cos(π/5)=формула cosα-cosβ=-2sin((α+β)/2)·sin((α-β)/2)= - 2sin(3π/10)sin(π/10)...