Question

Trb sa demonstrez ca e 1/2 va rooog

Answer 1

Răspuns:

Nu este = 1/2 ; - 1/2 ≠ 1/2

Explicație pas cu pas:

cos2π/9 + cos4π/9 + cos6π/9 + cos8π/9 = 1/2

2cosπ/3 × cos-π/9 + cos2π/3 + cos8π/9 = 1/2

2 × 1/2 × cosπ/9 - 1/2 + cos8π/9 = 1/2

cosπ/9 - 1/2 + cos8π/9 = 1/2

2cosπ/2 × cos-7π/18 - 1/2 = 1/2

2 × 0cos-7π/18 - 1/2 = 1/2

0 - 1/2 = 1/2

- 1/2 = 1/2 ; FALS