Question

Resolva a equação 2 × cos2 + cosx - 1 = 0

Answer 1

2cos²x + cosx - 1 = 0
Δ =1² -4.2.(-1)
Δ = 1 + 8 = 9
cosx = (-1-3)/4 = -1 ou
cosx = (-1 + 3)/4 = 1/2
P/ cosx = -1 => x = π + 2kπ, k ∈ Z
P/ cosx = 1/2 => x = π/6 + 2kπ, k ∈ Z