Răspuns:
2cosα (cosα-1)
Explicație pas cu pas:
1-2cosα+2cos²α-1=2cos²α-2cosα=2cosα (cosα-1)=
si , daca vrei sa continui...
2cosα (cosα-cosπ)= 2cosα*(-2sin(α/2-π/2)sin(α/2+π/2)=
4cosα*sin(π/2-α/2)sin(α/2+π/2)=
4cosα cos(α/2)sin(α/2+π/2)=
4cosα cos(α/2)sin(π/2-α/2)=
4cosα cos(α/2) cos(α/2)
=4cosα cos²(α/2)
