14 cosx-7 cos^2x = 0

Question

14 cosx-7 cos^2x = 0

Answer 1

14cosx - 7cos²x = 0
7cosx(2 - cosx) = 0
1) 7cosx = 0
cosx = 0
x = π/2 + πn, n ∈ Z
2) 2 - cosx = 0
cosx = 2 - нет решений, т.к. cosx ∈ [-1; 1].
Ответ: x = π/2 + πn, n ∈ Z.